Fan switch mis-information
1 Attachment(s)
THIS POST IS SPECIFICALLY AIMED AT THOSE STILL USING THE STOCK ECU.
I just learned something kind of critical today about fan switches in our cars after reading the wiring diagram for waaaay too long. What I learned is replacing the fan switch with one like the FC switch that is triggered at 95C instead of 105C only assists in cooling if any one of the other fan triggers has been turned on. In other words, an upgraded fan switch does not turn the fans ON sooner. It only makes the fans spin faster if they're already on. Look at the attached diagram. The fan switch relay is #3 on the far right. Notice that the switched side doesn't have a pole that comes from a 12V source. The switched side provides an additional ground to the fans. This means the fans would have to already have 12V going to them in order the completion of this circuit to get them turning when the fan switch is triggered. But below 105C, the fans don't have 12v going to them from any of the the other 3 relays so they remain off. Each of the relays only provides a 12v source to the fans when triggered (A/C = Relay #1, coolant temp > = Relay #2 & #4 What this effectively means is there isn't anything that can be done to get the fans (with a stock ecu) to be triggered by temp to turn on sooner than 105C. Yes, A/C can be turned on but then the fans efforts are being directed @ coolant AND the a/c condenser. I think what could be done is de-pin wire at the ECU that provides ground to trigger fan relays #2 and #4 and run it up to the wire from the fan switch. This should start the fans at 95C @ middle speed. I guess I have a project for tomorrow night. If I'm mistaken on my interpretation of the manual, please correct me and let know where I screwed up. |
Don't think I have seen that diagram before...... It's a good one lol. For a 2 speed fan, maybe try the fsm one
It loops back on its self and would blow if it would even run |
Very interesting! I think you may be on to something there.
I still think the FC thermoswitch is a good idea regardless. I can't remember what the temp is the stock ECU kicks the fans on, though. Dale |
Now that I've had some sleep, a couple more things.
In order to test this (at your own risk), run out to your car and disconnect the 4 relays. Don't worry they're all the same. The A/C connector is different, but I'm going to omit it for this test because I'm too lazy to explain how to test it AND the other 3 separately. With the KEY ON, Test the voltage across the larger wires in each of the remaining 3 connectors. You'll find that one of them doesn't have 12V (NOTE THIS CONNECTOR, IT IS THE FAN SWITCH CONNECTOR). At any point during this test, you can turn on your A/C and get another fan input for additional speed. Now create a jumper and jump the two larger wires on any one of those connectors (at your own risk). This simulates the relay being triggered and turns on your fan. Now that any one (or both depending on which connector you choose) of your fans is on, check the voltage across that terminal that didn't have 12V (fan switch). It should now have 12V, but that isn't high amperage 12V. It is the residual left over after your fan or fans have "taken their drink" from the 60AMP lead feeding them. Jumping the large wires on that connector will lead to a speed increase, because you're providing a path for that 12V with whatever current is left in it to go to ground. If you then jump the 3rd terminal, this will give you a larger speed increase than what the fan switch provided because it provides a 12v from a circuit before anything else has had a chance to "drink from it". I also realized that even PowerFC users can't use that trigger to turn on their fans. The fan control the PowerFC provides is for relay #2 and #4 which are individual triggers for each fan. If those are triggered @ 85deg and the FC thermo is installed, the end result will be: Low speed fans from 85C ---> med speed fans at 95C I think the only way to trigger the fans sooner without having programatic control from an ecu or having to use A/C is to simulate the electrical load input at the temperature that you want. The alternative would be modification to the temperature sensor signal, but that would result in timing and fuel changes. More to come if i figure out another trigger. |
1 Attachment(s)
Originally Posted by DaleClark
(Post 11778135)
Very interesting! I think you may be on to something there.
I still think the FC thermoswitch is a good idea regardless. I can't remember what the temp is the stock ECU kicks the fans on, though. Dale The fan switch triggers at 108C but that only helps because the fans are already on. |
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Makes me feel better about ripping all the cooling relays out last year and going after market
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Your post highlights the importance of being able to set the "fan on" temperature with the PFC. Once the fans are on, then the lower temperature control switch (as well as a/c or other electrical load) can kick them up to higher speeds at lower temps.
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IMHO this subject was pretty well covered in DaleClark's thread... but read all the posts for a complete understanding of the effect on overall cooling and the effect of Mazda's "cooling fan mod."
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Originally Posted by Mps_hell
(Post 11778356)
Makes me feel better about ripping all the cooling relays out last year and going after market
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Originally Posted by wstrohm
(Post 11780317)
IMHO this subject was pretty well covered in DaleClark's thread... but read all the posts for a complete understanding of the effect on overall cooling and the effect of Mazda's "cooling fan mod."
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Been years and years ago since I traced the relay functions, but what I remember is that the cars had a recall where Mazda changed the wiring setup, don't think the manuals portray as-modded. Only recourse is to test circuit logic.
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Originally Posted by Julian
(Post 11781175)
Been years and years ago since I traced the relay functions, but what I remember is that the cars had a recall where Mazda changed the wiring setup, don't think the manuals portray as-modded. Only recourse is to test circuit logic.
See the pun I made there? Yea, I'm pretty funny! :D |
I am 90% sure that I can hear the fans come on BEFORE 220F. unless my temp gauge is off by 20 degrees.. unfortunately my baby's at my mom's house until I finish this clutch job, but definitely will test this.
EDIT: running FC thermoswitch |
Just went out for a drive and my fans were turning on at 205-208F just before 210F with fc thermoswitch. Fans used to turn on at 220F before so not sure what your looking at but I think you could be wrong. Didn't have anything else on either like AC.
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Originally Posted by 00SPEC
(Post 11781822)
I am 90% sure that I can hear the fans come on BEFORE 220F. unless my temp gauge is off by 20 degrees.. unfortunately my baby's at my mom's house until I finish this clutch job, but definitely will test this.
EDIT: running FC thermoswitch
Originally Posted by 2slo4my7
(Post 11783901)
Just went out for a drive and my fans were turning on at 205-208F just before 210F with fc thermoswitch. Fans used to turn on at 220F before so not sure what your looking at but I think you could be wrong. Didn't have anything else on either like AC.
Thanks a bunch you guys. Just to confirm, where is your temp sensor located AND you're running with the stock ECU? |
I have the Pettit ECU which I don't think is any different for fan temps? Correct me if that's wrong.
Can't remember exactly which line the temp sensor is on but its located along the firewall behind intake/throttle body. Always been pretty accurate since, as I said, I used to see the fans kick on at 220F before FC thermoswitch. Someone also once told me that fans would kick on a couple degrees sooner if you turn the dash lights on.(not turning lights on completely but just one click on the light switch) Is there any truth to this? |
I'm asking where your temp sensor is at because I think we should be measuring at the same point. Measuring at different points can yield different readings. My sensor is in the upper radiator hose.
Yes turning on the parking lights activates the electrical load circuit which turns on the fans, but I don't remember where in the FSM it says how much sooner |
It is possible that we would have different readings. I hope my temp gauge isn't off by 10-15F though!
Was reading this thread again. Seems as though racerx7 is saying the same as you. Fan thread According to Dale's first post, turning on your parking lights would also only increase the fan speed and not make them turn on at a lower temp. So if you are both correct, can we simply not send power/ground from the thermoswitch to the proper relay in order to make the fans turn on at 95C? fooling it into thinking it is getting a reading from the ECU Seems odd since I'm pretty sure I remember a difference in temp when I did the thermoswitch mod. I could be wrong since it was 4-5 years ago. |
I see what you are saying, OP, but as usual, Mazda is correct. Based on the FD wiring manual (Z42 B-2), as well as the summary you copied, there are 3 connections to each motor to control speed (motors run in parallel, as a single fan motor ). The catch is one of the connections is a gnd, and the 2 others are 12V inputs. That leaves the 4th connection as a permanent gnd. Also, three of the relays have 12V supplies, vs relay 1 for the AC input ... it has an ignition hot for the relay's coil.
SOoooo, when the fan switch is closed / grounded, it provides a gnd to the motors by way of relay-3, resulting in med speed. The voltage for the motors comes from relays 2 & 4, with a gnd from the fan control module or the ecu. I have the "fan switch mod", where I have an extra switch that grounds the test lead of the fan-control-module, which is like closing the FC switch to gnd. I just went out and turned the ign on (AC off), and engaged the switch and the fans came on at medium speed, per the Mazda manual test proceedure. If you run them for more than 150 sec, and turn off the switch, the speed drops to low. This is all done by the fan control module, that was added in 1993 models so fans could stay on after the ign was off. This is my post from a 2005 thread about the FC switch: https://www.rx7club.com/3rd-gen-arch...6/#post4607146 ------------------------------------------------------------------------------ "However, I am perplexed as to why I have a 115 degree switch? Maybe because of the automatic tranny?" Me -> This is a separate trans switch for autos, located where one of the plugs normally resides in the fill neck hsg. If coolant hits 240F, atx logic engages torque converter lock-up more often, to reduce heat from torque converter. You still have 108C fan switch, behind t-stat. Replacing with FC-or-miata switch means, with ac off, fans come on 1st at 207F at med speed, vs 221F (ecu controlled) at slow speed then 226F at med speed. Note this may only change med speed trip to 221F for some. Alternative is to run with parking lights on, or cabin fan at 3 or more, in hot traffic. This trips fans on slow at about 200-210F. -------------------------------------------------------------------------------------- The previous link, by Dale Clark, describes correctly the sequence of operation. . |
Originally Posted by KevinK2
(Post 11787585)
SOoooo, when the fan switch is closed / grounded, it provides a gnd to the motors by way of relay-3, resulting in med speed. The voltage for the motors comes from relays 2 & 4, with a gnd from the fan control module or the ecu. . |
Originally Posted by KevinK2
(Post 11787643)
Correction, the fan switch grounds the coil for relay 3, which then provides grounds for the fan motor relays 2 and 4. With a stock fan thermo switch, it provides the lowest temperature (221F) where the fans come on low speed. The FC switch lowers that initial fan operation temperature. Then when the temp rises to 226F, the ecu uses another thermo-sensor to set the fan speed at medium. Not if the AC is ON, those speeds will be "up 1", so cold coolant results in low speed, fan switch triggers med speed, and the high temp 226F to ecu gets fast speed.
. This entire explain is with A/C turned off!!! For the fans to get activated by temp, the thermosensor (only 1 on the car) not thermoswitch (also only 1 on the car) has to report 221F like you said. I'm sorry, but the way I read that diagram is that the fan switch (thermo switch) provides a ground for the coil on relay 3 (you and i agree here). This then provides an additional ground for both FANS, not the fan relays. Look again at the diagram in the first post. The right side of relay 3 only serves to connect the bottom right leg of each fan to ground (no connection to a relay). So if you consider the fans in an off state at 220F. At 221F the ECU simultaneously triggers relay #2 (which provides 12V to fan 1)and #4 (which provides 12V to fan 2) based on input from the thermosensor. That is speed input 1. At 226F the stock thermoswitch activates providing ground for the coil in relay 3 which then provides a ground to both fans (not their relays). This is speed input 2. Now, if you consider the fans in an off state at 94 deg C (201F) and the FC thermoswitch activates at 95 deg C (203F), providing a ground to the coil on relay 3 which then provides a ground to each fan. Realize that at that moment each fan has 0V coming in on each of its two inputs (top left and top right of each fan in the diagram) because the relays #2 and #4 won't get triggered until the thermosensor reports 221F to the ECU. Remember, relay #3 only provides a ground, not a 12V source to the fans. So the fans will stay off. But when they do get activated by the ECU when the thermosensor finally reports 221, the fans will engage at speed 2. I didn't make any claims about Mazda being wrong. I just stated that we've (the FD community) been reading the FSM incorrectly and assuming that putting in an FC thermoswitch makes fans come on sooner. It most certainly does not. |
Originally Posted by Boost Lee
(Post 11787912)
This entire explain is with A/C turned off!!!
For the fans to get activated by temp, the thermosensor (only 1 on the car) not thermoswitch (also only 1 on the car) has to report 221F like you said. I'm sorry, but the way I read that diagram is that the fan switch (thermo switch) provides a ground for the coil on relay 3 (you and i agree here). This then provides an additional ground for both FANS, not the fan relays. Look again at the diagram in the first post. The right side of relay 3 only serves to connect the bottom right leg of each fan to ground (no connection to a relay). So if you consider the fans in an off state at 220F. At 221F the ECU simultaneously triggers relay #2 (which provides 12V to fan 1)and #4 (which provides 12V to fan 2) based on input from the thermosensor. That is speed input 1. At 226F the stock thermoswitch activates providing ground for the coil in relay 3 which then provides a ground to both fans (not their relays). This is speed input 2. Now, if you consider the fans in an off state at 94 deg C (201F) and the FC thermoswitch activates at 95 deg C (203F), providing a ground to the coil on relay 3 which then provides a ground to each fan. Realize that at that moment each fan has 0V coming in on each of its two inputs (top left and top right of each fan in the diagram) because the relays #2 and #4 won't get triggered until the thermosensor reports 221F to the ECU. What I have written, and tested, is that by adding the FC temp switch, you LOOSE the slow speed function, and what was the control for the higher temp (fan switch) is now the control for the lower temp. I just tested with my cabin fan switch, in parallel with the water thermo switch. With eng cold, ign on, I turn on switch and fans come on at med speed. Turn on AC too and I got high speed. So I disagree with you, in that the fans will come on at a lower temp with the FC switch. You just loose low speed. Remember, relay #3 only provides a ground, not a 12V source to the fans. So the fans will stay off. But when they do get activated by the ECU when the thermosensor finally reports 221, the fans will engage at speed 2. I didn't make any claims about Mazda being wrong. I just stated that we've (the FD community) been reading the FSM incorrectly and assuming that putting in an FC thermoswitch makes fans come on sooner. It most certainly does not. In the FSM, there is a test for the oem thermo switch. At 214F, .5 ohm max (closes). At 226F, 1 Meg ohm min (open ! ). Something to think about ... don't need relay 3 for fan control if temps above 226F. . |
Kevin, when you post a correction, I take that as meaning that the reader is supposed to ignore your previous statement, right? Well, I did that and addressed the statement that you said was the "correct one". Now you're correcting the correction... there's a bit of clutter here man!!!
Ok, with that said, let's move on. My first statement in my previous post "This entire explain is with A/C turned off!!!" was to indicate that I was describing the behavior of the car with the A/C off. I wasn't commenting on your previous post.
Originally Posted by KevinK2
(Post 11788139)
I'm not sure where you find that ecu logic that does not allow the motor relays to be actuated by grounds. The ecu sends voltage to the motors by providing a gnd to fan relays 2 & 4, and that is for all operating modes.
Originally Posted by KevinK2
(Post 11788139)
The thermoswitch for medium speed at T2 closes to allow an extra ground to the motor.
Instead of debating how the rest of the fan system works, focus on the heart of the matter which is: With all other fan inputs turned off, do the fans turn on at lower speed or when the FC Thermoswitch provides a ground to relay #3 at 201F instead of 226F (stock thermoswitch activation temp)? I say no, you say yes. If you agree the above statement is the issue, please walk us through the wiring diagram for what happens when the thermoswitch is triggered. |
Again I apologize for my disruptive "correction to a correction". No excuse,
guilty as charged. We agree on most of this, but the key to the discussion is as you just said in bold. But before that, you had questions about my last post, with two quotes in your last post: 1st quote, This was about your prior statement that when an FC switch is about to turn on a fan, you said "Realize that at that moment each fan has 0V coming in on each of its two inputs" . I questioned how you knew there was zeo volts at the 2 motor inputs. Yes, one input is for AC-on only, but the other one will see voltage if the ecu provides the relay's ground. There is nothing in the FSM-wiring that suggests the ecu will not provide the relay ground in this case. As I said before, I have a new switch parallel to the fan-switch. With engine COLD and off, ign on, I could turn the fans on medium speed with that switch on. And when I turned the AC on too, fans went to fast speed. That test supports what I have been saying ... there is voltage at the non-ac motor input most/all the time ign is on. 2nd Quote, With more explanation: (AC off) The OEM thermo-switch for the call for medium fan speed at the 2nd tempeature point (226F), closes at that temp to allow the variable ground at the motor to close. The other motor ground is permanent. I hope that clears it up for you. Now for your question in "bold" text: "With all other fan inputs turned off, do the fans turn on at lower speed or when the FC Thermoswitch provides a ground to relay #3 at 201F instead of 226F (stock thermoswitch activation temp)?" As I said before, with the FC switch, the fans come on at med speed at about 202F, and apparently override the normal ecu low speed on at 221F. And I never said yes to that question in any form. But from your 1st post: What I learned is replacing the fan switch with one like the FC switch that is triggered at 95C instead of 105C only assists in cooling if any one of the other fan triggers has been turned on. In other words, an upgraded fan switch does not turn the fans ON sooner. It only makes the fans spin faster if they're already on. I bought the FC switch, but did not install it. I felt that it would turn on the fans just as the t-stat was wide open, and needlessly cool the radiator contents to about 185F before it turned off, wasting the fan motor run time. If there were a 215F switch, I'd go with it. For now, I use my extra switch to turn on the fans when I know coolant is heating up toward 221F. I even put a resister in parrallel with the temp-sensor for the gauge, so it shoots up when the temp exceeds 226F. Handy at track events. I just tested the FC switch, and it closed at 202F, and opened again at about 185F. . |
Originally Posted by KevinK2
(Post 11788662)
I bought the FC switch, but did not install it. I felt that it would turn on the fans just as the t-stat was wide open, and needlessly cool the radiator contents to about 185F before it turned off, wasting the fan motor run time. If there were a 215F switch, I'd go with it. For now, I use my extra switch to turn on the fans when I know coolant is heating up toward 221F. I even put a resister in parrallel with the temp-sensor for the gauge, so it shoots up when the temp exceeds 226F. Handy at track events.
I just tested the FC switch, and it closed at 202F, and opened again at about 185F. Are you sure the fans would turn off at 185F? I have the FC thermoswitch and the fans turn on at around 205-207F on my gauge (reading from TB line) so probably real temp of 202F but then turn off again at around 200F on my gauge or again real temp of 195F since my gauge seems to read warm by about 5F. |
The FC thermoswitch I tested was N350-18-840, could it be different vs yours? I tested it twice, and both times with a slow cool it changed back to open as it hit 185F on the way down.
If you have the stock T-stat, full open at 203F, it could be that as the coolant cooled, the T-stat started closing. Beyond that I would have to check my spare waterpump housing to see if the bypass line is pulled from the back of the block, with more stable temps, vs where the switch is perhaps influenced by water returning from the radiator. Could take a while. . |
Originally Posted by Boost Lee
(Post 11788491)
Instead of debating how the rest of the fan system works, focus on the heart of the matter which is:
With all other fan inputs turned off, do the fans turn on at lower speed or when the FC Thermoswitch provides a ground to relay #3 at 201F instead of 226F (stock thermoswitch activation temp)? I say no, you say yes. If you agree the above statement is the issue, please walk us through the wiring diagram for what happens when the thermoswitch is triggered. And, you can search for a copy of the circuit diagram, Z-42, B-2, from the 1993 wiring Diagram workbook. . |
Originally Posted by KevinK2
(Post 11788752)
The FC thermoswitch I tested was N350-18-840, could it be different vs yours? I tested it twice, and both times with a slow cool it changed back to open as it hit 185F on the way down.
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Hello again Kevin! I've come to like these evening exchanges!!!
To answer your question about the fans having 0V on their inputs... Think about it, like you said, there is a constant ground to both of the fans. If 12V was ever applied to either of the inputs, then the fans would turn on.
Originally Posted by KevinK2
(Post 11788662)
That test supports what I have been saying ... there is voltage at the non-ac motor input most/all the time ign is on.
2nd Quote, With more explanation: (AC off) The OEM thermo-switch for the call for medium fan speed at the 2nd tempeature point (226F), closes at that temp to allow the variable ground at the motor to close. The other motor ground is permanent. By the way, I agree there is a permanent ground on each fan and the thermoswitch triggers the second ground via relay #3. If your statement above that I quoted above were true, in that: a) The fans have a permanent ground (I agree) b) There is 12V "most/all" the time to the fans (I disagree) Then the fans would run "most/all" the time from Key On, right? But they don't, so it appears that you are incorrect. I just went out and performed a test to confirm what the wiring diagram suggests (0V at the fans until an input is triggered). I looked for 12V going to any of the 4 wires going to each of the fans... with the Key On, Engine Off. None of the 4 wires had voltage. I then ran the engine, and again none of the 4 wires had voltage. This proves that the fans do not receive any voltage when there are no inputs, it also proves that the ground provided to the fans when the FC thermoswitch and subsequent relay are activated will not turn on the fans because there is no voltage going to the fans at Key On. Now... I've read through the rest of your post and agree with somethings you said (The FC switch does indeed eliminated the low speed) but realized that you didn't even install the FC Thermo switch, which means you're commenting on this topic based on your theory of what is happening rather than commenting on your experience of what actually happens (which I feel I am doing). I think we should be comparing the same thing instead of going back and forth in a theory vs. application discussion. Could you please test your car and then verify / reject the following (no theory, actual test): 1)In an OEM wiring configuration there isn't 12V going to the fans "most/all" the time. 2)In an OEM wiring configuration triggering the fan switch (with all other inputs turned off) does NOT turn on the fans. If you like, we can talk on the phone and clear this up so that we can post our findings rather than the ongoing deliberation. |
Originally Posted by KevinK2
(Post 11788777)
Going back to your post, you ask an "either or" question, and then want a yes or no response. Mr Lee, you have a habbit of not being specific enough for me to understand what you are wanting to say.
And, you can search for a copy of the circuit diagram, Z-42, B-2, from the 1993 wiring Diagram workbook. . With all other fan inputs turned off, do the fans turn on at lower TEMP when the FC Thermoswitch provides a ground to relay #3 at 201F instead of 226F (stock thermoswitch activation temp)? Yeah, that was totally unclear before! BTW the diagram you refer to is attached to the first post in this thread. |
Originally Posted by Boost Lee
(Post 11788988)
Hello again Kevin! I've come to like these evening exchanges!!!
To answer your question about the fans having 0V on their inputs... Think about it, like you said, there is a constant ground to both of the fans. If 12V was ever applied to either of the inputs, then the fans would turn on. Your statement that there is voltage to the fans most/all the time is not supported by the wiring diagram. The whole point of relay #1, #2 and #4 is to provide 12V to the fans when an input is triggered. If the configuration you're eluding to is what you've experienced, then it suggests is that your wiring has been modified from the factory configuration. By the way, I agree there is a permanent ground on each fan and the thermoswitch triggers the second ground via relay #3.
Originally Posted by Originally Posted by KevinK2
That test supports what I have been saying ... there is voltage at the non-ac motor input most/all the time ign is on.
2nd Quote, With more explanation: (AC off) The OEM thermo-switch for the call for medium fan speed at the 2nd tempeature point (226F), closes at that temp to allow the variable ground at the motor to close. The other motor ground is permanent. If your statement above that I quoted above were true, in that: a) The fans have a permanent ground (I agree) b) There is 12V "most/all" the time to the fans (I disagree) Then the fans would run "most/all" the time from Key On, right? But they don't, so it appears that you are incorrect. I just went out and performed a test to confirm what the wiring diagram suggests (0V at the fans until an input is triggered). I looked for 12V going to any of the 4 wires going to each of the fans... with the Key On, Engine Off. None of the 4 wires had voltage. I then ran the engine, and again none of the 4 wires had voltage. This proves that the fans do not receive any voltage when there are no inputs, it also proves that the ground provided to the fans when the FC thermoswitch and subsequent relay are activated will not turn on the fans because there is no voltage going to the fans at Key On. Now... I've read through the rest of your post and agree with somethings you said (The FC switch does indeed eliminated the low speed) but realized that you didn't even install the FC Thermo switch, which means you're commenting on this topic based on your theory of what is happening rather than commenting on your experience of what actually happens (which I feel I am doing). I think we should be comparing the same thing instead of going back and forth in a theory vs. application discussion. Could you please test your car and then verify / reject the following (no theory, actual test): 1)In an OEM wiring configuration there isn't 12V going to the fans "most/all" the time. 2)In an OEM wiring configuration triggering the fan switch (with all other inputs turned off) does NOT turn on the fans. If you like, we can talk on the phone and clear this up so that we can post our findings rather than the ongoing deliberation. Did you miss this valuable input?
Originally Posted by 2slo4my7
(Post 11788726)
...... I have the FC thermoswitch and the fans turn on at around 205-207F on my gauge (reading from TB line) so probably real temp of 202F ......
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Originally Posted by Boost Lee
(Post 11788993)
....BTW the diagram you refer to is attached to the first post in this thread.
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Hey Kevin
Originally Posted by KevinK2
(Post 11789159)
Nope. You don't undersatand the diagram fully. The ecm, with IGN on ( which I hope is what you mean by "key on" ... two clicks) is capable of providing gnds to the motor relays. Try grounding terminal B on relay #3, and turning key to ign on. Fans shoul run at med speed. Just run a few sec's. They may carry on 10 minutes at lower speed with gnd removed and IGN off, based on the FCM.
Originally Posted by KevinK2
(Post 11789159)
You are forgetting that the fans are also controlled by providing a ground to the motors, by way of relay #3 and the fan switch. The voltage to the motors may turn on at that point, by way of the ecu, or it may be there already.
When relay #3 is triggered and the resulting ground is applied to the fans, where does the required 12V source to the fans come from? What triggers it? Please explain the path of items triggered to make that happen. Please post the wiring diagram that supports your statement. I wonder if you and I are looking at different reference material. |
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Hey Kevin
Originally Posted by Kevin
Nope. You don't understand the diagram fully. The ecm, with IGN on ( which I hope is what you mean by "key on" ... two clicks) is capable of providing gnds to the motor relays. Try grounding terminal B on relay #3, and turning key to ign on. Fans shoul run at med speed. Just run a few sec's. They may carry on 10 minutes at lower speed with gnd removed and IGN off, based on the FCM.
Response: When I said "gnd to connector B" , did you just pull the connector off and provide a ground to the B position? What you have to do is make jumpers for all the connections, with a Y on the B connector that you put to ground. Did you make all these jumpers? I have done the same thing for other connectors where I wanted to gnd one of the terminals. It is obvious that you need to make the jumpers, to avoid unplugging all 4 wires in the relay.
Originally Posted by Kevin
You are forgetting that the fans are also controlled by providing a ground to the motors, by way of relay #3 and the fan switch. The voltage to the motors may turn on at that point, by way of the ecu, or it may be there already.
Response: You just repeated what I said in the 1st sentence, and did not read my 2nd sentence: "The voltage to the motors may turn on at that point, by way of the ecu, or it may be there already." When relay #3 is triggered and the resulting ground is applied to the fans, where does the required 12V source to the fans come from? What triggers it? Please explain the path of items triggered to make that happen. Response: For the ~4th time ... LOOK at your wiring diagram from the 93 Service Highlights, and the gnd provided by the ecm or FCM. Please post the wiring diagram that supports your statement. I wonder if you and I are looking at different reference material. There is a ground line for the two motor relays that comes from the ECM, on the lower right corner. When grounded, the motor relays provide voltage to the motors. Response: There is nothing of significance in my 93 Factory Wiring Diagram that is not shown in the diagram you have, and it supports my statement. It is consistent with my test with ign on, engine off, tripping the fan-switch gnd (with another parallel switch) turns on the fans. Comment: At this point it obvious you are not experienced in this specific type of auto wiring diagram interpretation. In spite of my repeated references to the ecu and it's grounding function for the relays, you don't get it. Most important, you ignored this comment I made: Originally Posted by 2slo4my7 ...... I have the FC thermoswitch and the fans turn on at around 205-207F on my gauge (reading from TB line) so probably real temp of 202F ...... That data completely blows away your purpose for this flawed thread, in that adding the FC switch DOES lower the temps when the fans come on. . |
Boost Lee,
At this point the discussion has become repetitive, as it seems you do not read my responses completely as of late. You did find a couple of mistakes I made, but I corrected them and they were done with, not returning as an issue again and again. Please read thoroughly before responding. Thanx, Kevin BTW, rather than make the jumpers to gnd that terminal, you can do the same thing by just grounding the black "test wire pigtail" that comes from the FCM, behind the ecu on the right kick pannel on the passenger side. This is the wire I used for my extra "on demand" fan switch. . |
I did not disconnect the connector from the relay, I used an alligator clip and jumped wire B to ground while still connected to the relay. I even tried grounding the pigtail near the ECU.
I've repeated myself because you've not answered my question. When the thermoswitch is triggered it provides a ground to relay #3, and your statement that the ECU then somehow provides 12V isn't proven by anything. My test last night didn't prove it. I've looked at the diagram to see if somehow the ECU is aware of the thermoswitch being triggered and there's no connection between the thermoswitch and the ECU. So how is it possible for the ECU to trigger relay #2 and #4 when the thermoswitch is triggered when the ECU is not aware of the thermoswitch? I've asked a few times for you to post the reference material you're using so I can see the documentation you get your perspective from, but instead you've asked me to perform tests which I've done, and both had results that were contrary to your statements. You conceded on the first, and I'm waiting on the second. All I'm asking from you is the documentation you're using to make the statement that the thermoswitch magically alerts the ECU to provide 12V to the fans (via relay or whatever). I just don't see it. I'm perfectly able to read a wiring diagram, I just can't infer something that hasn't been shown. We've gone at this for a few days without throwing insults at each others ability or logic. We're both ready to end this, but let's try and keep the civility going! BTW I'm using a 94 diagram for my 94 car not a 93. 2slo4my7 isn't using a stock ECU, he's using a Petit ECU unit. Because of this, I can't assume the same situation applies to him, so I won't include his response. Let's finish this off and prove that people coming from two different perspectives can actually arrive at the truth on the Internet. BTW as a result of yesterdays test, I made a modifcation to my car. On the connector that goes to the fan control module, I connected the wire from the thermoswitch to the wire that provides ground for relay #2 and #4 using a jumper. This now allows the thermoswitch to provide ground to relay #2, #3, #4 at the same time. My fans now come on @medium speed when the thermoswitch is triggered. I left that connector disconnected from the fan control unit for now. |
It appears I'm not the only one who realized this!
https://www.rx7club.com/3rd-generati...g-fans-462760/ |
Ok, I see the source of the repitition. Including the 2 trigger link, there are 3 different wiring diagrams from the Factory wiring manual in play now:
1) Yours on page 1, post 1 2) The one on Two Trigger Fans 3) My 93 diagram, which is the same as the section F of the 93 "highlights" diagram on post#5 I'm sorry I said you could not read the diagram correctly, we were NOT looking at the same one. If you look at post 5, that is what I was refering too in this thread. That includes the fan control recall, that includes the FCModule shown on the right. This should make more sense to you, as there is a gnd wire going to the ecm. About the Pettit ecu, I have a similar one from the expired "XS Engineering" (not installed now). They install a motherboard that will except the plugin boards with different boost, timing, and fuel maps. That's it. There is no change in how the fans work. It was provided by Techtom, who made the parts an about 4 different "daughter" board chips, based on what other mods were done to the engine, intake, and exhaust. And perhaps that explains most of our differences. But we have a 94 where the fans turn on at 203 with the FC switch (with chipped board), and my 93 where I can simulate the switch closing at cold conditions. . |
Originally Posted by Boost Lee
(Post 11789805)
BTW as a result of yesterdays test, I made a modifcation to my car. On the connector that goes to the fan control module, I connected the wire from the thermoswitch to the wire that provides ground for relay #2 and #4 using a jumper. This now allows the thermoswitch to provide ground to relay #2, #3, #4 at the same time. My fans now come on @medium speed when the thermoswitch is triggered. I left that connector disconnected from the fan control unit for now.
Some people on here are very fast to repeat what someone else told them with out trying to find out for them self what their own car is doing. I have two daviescraig Thermatic Switch (Part No: 0400). It is a work in progress for me however you seem to be on the same path I was on till I got the shits and cut the lot out. I can however tell you that despite what people on here like to tell you it is possible to get way more cooling out of the stock rad set up on these cars with a 75C thermostat and better relays ( at one point I couldn't get my car over 80c in town stop and go traffic driving like a twat) Your getting closer to solving the cooling issues.:nod: I can feel the dark side within you:lol: you will also find that the stock wiring..... like the rest of the car wiring is a pos and gets hot when running speed 2 and even hotter on speed 3 |
One thing that derailed our communication was that the diagram in post 5 was just like mine, and not like your diagram in post 1. I did not hear anything about them being different, so I thought you were using that diagram, like mine. Glad you got your model to work like at least 2 other cars.
Do you think that it was possible your fans would come on early with the FC switch, based on the 150 sec delay when tested indirectly? You heard a click ... could have been a timer. Recall Test Proceedure: In my notes, I copied a test proceedure from the recall #60504 TSB for checking out the FCM. The first part says to gnd the test wire (parallel with switch) and fan comes on 150 sec AFTER you turn ign on. It also notes that before Apr 1 93, P0210660, fan operates with no delay And after that date, P0210661, fan comes on 100-150 sec after key on. I assume this is for the test proceedure only. . |
1 Attachment(s)
Originally Posted by KevinK2
(Post 11789877)
Ok, I see the source of the repitition. Including the 2 trigger link, there are 3 different wiring diagrams from the Factory wiring manual in play now:
1) Yours on page 1, post 1 2) The one on Two Trigger Fans 3) My 93 diagram, which is the same as the section F of the 93 "highlights" diagram on post#5 I'm sorry I said you could not read the diagram correctly, we were NOT looking at the same one. If you look at post 5, that is what I was refering too in this thread. That includes the fan control recall, that includes the FCModule shown on the right. This should make more sense to you, as there is a gnd wire going to the ecm. About the Pettit ecu, I have a similar one from the expired "XS Engineering" (not installed now). They install a motherboard that will except the plugin boards with different boost, timing, and fuel maps. That's it. There is no change in how the fans work. It was provided by Techtom, who made the parts an about 4 different "daughter" board chips, based on what other mods were done to the engine, intake, and exhaust. And perhaps that explains most of our differences. But we have a 94 where the fans turn on at 203 with the FC switch (with chipped board), and my 93 where I can simulate the switch closing at cold conditions. . OK Onward!!!! I think I get your perspective now that I've looked at that diagram. You're saying that the thermoswitch state is sent to the FCM which is also connected to the ECU and then the ECU or FCM then provide the ground to activate relay #2 and #4? Ok. The thermoswitch is connected to FCM pin C. The FCM pin E is connected to ECU pin 3D. But it's marked as an output by the service manual (documentation attached). To me this means the ECU doesn't read signal from this wire and there is no logic performed by the ECU based on the state of signal on 3D. So I concluding the thermoswitch wouldn't have any impact on the ECU. The diagram in post #5 doesn't show another thermoswitch connection to the ECU, even proxied by another device. Do you agree? This leaves the FCM as the only item that can trigger the fans. In order for the FCM to switch relay #2 and #4, it would need to internally connect pin E to ground. But wait...last night I had to make a jumper that did EXACTLY that. (I referred to it in post #38. So I think here are the options: 1) I have a bad FCM, which blows my entire thesis out of the water and I owe you a set of FD spark plugs (that was the bet I made in my head) 2) The cars you've been playing with have a minor modification from stock and you owe me a Ferrari 458 (that was the other half of the bet I made in my head) Does what I've whittled it down to sound reasonable? (With the exception of the 458... a Tesla will do) :lol: I don't know the normal behavior of the FCM and there's no reference that I've found. SO... how do we test it? |
I didn't know there was a timer. I gotta test the timer!!!!!
|
Ok... So I applied the ground and then did the Key On... no Fans.
However, just days ago my car did keep the fans going for about 10 minutes after i shut it off warm, suggesting that the FCM was functioning then. I suppose I'll need to find another one to test with, huh? |
Originally Posted by KevinK2
(Post 11789877)
About the Pettit ecu, I have a similar one from the expired "XS Engineering" (not installed now). They install a motherboard that will except the plugin boards with different boost, timing, and fuel maps. That's it. There is no change in how the fans work. It was provided by Techtom, who made the parts an about 4 different "daughter" board chips, based on what other mods were done to the engine, intake, and exhaust. I installed an FC thermoswitch in July of 2007. It worked for me, like it has for so many others. I cant comment on why it works, I just know it does. |
Originally Posted by Mps_hell
(Post 11789896)
Some people on here are very fast to repeat what someone else told them with out trying to find out for them self what their own car is doing. I have two daviescraig Thermatic Switch (Part No: 0400). It is a work in progress for me however you seem to be on the same path I was on till I got the shits and cut the lot out.
I can however tell you that despite what people on here like to tell you it is possible to get way more cooling out of the stock rad set up on these cars with a 75C thermostat and better relays ( at one point I couldn't get my car over 80c in town stop and go traffic driving like a twat) Your getting closer to solving the cooling issues.:nod: I can feel the dark side within you:lol: you will also find that the stock wiring..... like the rest of the car wiring is a pos and gets hot when running speed 2 and even hotter on speed 3 |
Originally Posted by Boost Lee
(Post 11789950)
Ok... So I applied the ground and then did the Key On... no Fans.
However, just days ago my car did keep the fans going for about 10 minutes after i shut it off warm, suggesting that the FCM was functioning then. I suppose I'll need to find another one to test with, huh? The timer is in the FCM. It will run at med speed until temp is below 221 (FD switch) then it finishes at low speed. |
Billion - Performance Thermostats - Nengun Performance
Mine was in the car when i came from japan. I am using an 82c one ATM but like i said I am still working on it |
A vote for the FCM
When I used the FD for some DD duties, I was glad I had the "fan mod" switch that allowed me to park the car in some open lot in the sun on a hot summer day. I used the left position oem console switch to gnd the FCM test wire. Turn switch on (closed) ~2 minutes before arrival, and then turn it off, when parked and fan would run on at mid speed for near 10 minutes, switching to low speed, then turned off. You could feel the hot air exiting from under the car. Also handy when cooling down in the pits after a 20 minute track session with lots of WOT running. . |
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