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I've had an issue for a while now where my fans will only come on with the AC turned on or when the temp hits 206F (I have an FC thermoswitch). I have it set to about 85C in the PFC but it won't kick them on. It's not a huge deal because when I'm moving, my temps only get to around 170F these days, since it's fall and I have a fully ducted VMIC setup. Even when it wasn't ducted it would only get to around the same temps, or maybe up to 185F, but it was in the summer. Also, my temps have been coming up pretty slow lately. I ran the car up the other night to see when exactly the fans come on and I fell asleep three times sitting in the car waiting for it lol. Needless to say it took a while. Anyway, I usually switch the AC on (removed AC a few years ago) if I see it get to around 195-200F anyway, and if I don't catch it the thermoswitch does, so like I said, it's not a huge deal but I'd still like to get it fixed because it's not right.
In any case, I figured it might be due to Relays 2 and 4, so I tested them by jumping GND and TFA in the diagnostics box and the relays and fans kicked on. I've been talking to a friend that is an electrical engineer and FD owner and he told me to check for voltage (with the key on) at 3D, section 3 and 2nd wire over, but I checked to see which one it was in the FSM, on page Z-30, and I don't have that wire anymore, if it's any of the ones I'm thinking it is. Also, I was told by someone else that it was in the chassis harness but this one is in the engine wiring harness and I had stripped it down for a single turbo setup a year or two ago. Unfortunately, I don't know for sure that I've had this issue since then or not.
I thought maybe it was the thermoswitch, but the fans turn on at 206F so it's not that. My engineer buddy (I think he's on this forum but I don't know his name on here) has what he calls Frankenstein, that hooks between the ECU and connectors and has LEDs to tell you what's going on, and I'm thinking of meeting up with him tomorrow to use it.
Anyone have any ideas or have this problem before?
I've had an issue for a while now where my fans will only come on with the AC turned on or when the temp hits 206F (I have an FC thermoswitch).
I thought my fans where not working. I thought my car was over heating because the digital autometer was way off.
I bought a tool that allowed me to replace the radiator cap with a mechanical temp gauge.
Before I bought the tool I checked my fans and relays.
I took out each relay, applied power/ground and checked continuity between the other two poles. There where all fine.
To test the wires & fan I grounded each relay ( I should have just done this in the first place because it test the relay/wiring/fan all at once).
I know blah, blah, blah. I am getting to my point. I grounded relay, 1,2,4 one at time. they turned on my fans just like there suppose to. When I grounded relay #3 nothing happen. I switched relays, the wiring harness for relay #3 still did nothing. argg....
If you look at wiring diagram that I colored for you closer when you ground # 3 relay if the other relays are open it does NOTHING. hahaha. It took me a while to see it.
The fastes way to test relay # 3 is to turn on your AC, fans will come on low, then ground relay # 3 your fans will then go to med speed.
I think 99% people who install the fc/petti switch don't realize it really does nothing. Yes, I know it turns your fans on from low to med speed but it does NOT turn on your fans sooner. If your fans are already on low going to med does not make much of difference if any. Going from your fan off to low fan is MAJOR difference.
I am seriously thinking about rewiring my fans where the thermo switch turns on the fans ( like how they used to do it ). That way what ever thermo switch you choose will turn ON fans at that temp.
I thought my fans where not working. I thought my car was over heating because the digital autometer was way off.
I bought a tool that allowed me to replace the radiator cap with a mechanical temp gauge.
Before I bought the tool I checked my fans and relays.
I took out each relay, applied power/ground and checked continuity between the other two poles. There where all fine.
To test the wires & fan I grounded each relay ( I should have just done this in the first place because it test the relay/wiring/fan all at once).
I know blah, blah, blah. I am getting to my point. I grounded relay, 1,2,4 one at time. they turned on my fans just like there suppose to. When I grounded relay #3 nothing happen. I switched relays, the wiring harness for relay #3 still did nothing. argg....
If you look at wiring diagram that I colored for you closer when you ground # 3 relay if the other relays are open it does NOTHING. hahaha. It took me a while to see it.
The fastes way to test relay # 3 is to turn on your AC, fans will come on low, then ground relay # 3 your fans will then go to med speed.
I think 99% people who install the fc/petti switch don't realize it really does nothing. Yes, I know it turns your fans on from low to med speed but it does NOT turn on your fans sooner. If your fans are already on low going to med does not make much of difference if any. Going from your fan off to low fan is MAJOR difference.
I am seriously thinking about rewiring my fans where the thermo switch turns on the fans ( like how they used to do it ). That way what ever thermo switch you choose will turn ON fans at that temp.
I thought my fans where not working. I thought my car was over heating because the digital autometer was way off.
I bought a tool that allowed me to replace the radiator cap with a mechanical temp gauge.
Before I bought the tool I checked my fans and relays.
I took out each relay, applied power/ground and checked continuity between the other two poles. There where all fine.
To test the wires & fan I grounded each relay ( I should have just done this in the first place because it test the relay/wiring/fan all at once).
I know blah, blah, blah. I am getting to my point. I grounded relay, 1,2,4 one at time. they turned on my fans just like there suppose to. When I grounded relay #3 nothing happen. I switched relays, the wiring harness for relay #3 still did nothing. argg....
If you look at wiring diagram that I colored for you closer when you ground # 3 relay if the other relays are open it does NOTHING. hahaha. It took me a while to see it.
The fastes way to test relay # 3 is to turn on your AC, fans will come on low, then ground relay # 3 your fans will then go to med speed.
I think 99% people who install the fc/petti switch don't realize it really does nothing. Yes, I know it turns your fans on from low to med speed but it does NOT turn on your fans sooner. If your fans are already on low going to med does not make much of difference if any. Going from your fan off to low fan is MAJOR difference.
I am seriously thinking about rewiring my fans where the thermo switch turns on the fans ( like how they used to do it ). That way what ever thermo switch you choose will turn ON fans at that temp.
I'll probably go ahead and check my relays this way just in case, but it all makes sense. Just to be clear, these are the four relays in the rubber boots and bolted to the passenger side of the engine bay behind the light? My rubber boots are pretty fragile so I haven't gotten into them yet, but I'm going to have to in order to put my mind at ease about this. My fans work with the AC on, but how exactly did you ground relay #3? Actually how did you ground each relay? I'm just wondering if all the wires are connected to the relay, how do you ground it? Maybe I'm just having a brain fart right now lol. Not much sleep over the last few days.
I love the idea of wiring it so the thermoswitch turns on the fans. I was under the impression that's what they already did.
I'll probably go ahead and check my relays this way just in case, but it all makes sense. Just to be clear, these are the four relays in the rubber boots and bolted to the passenger side of the engine bay behind the light? My rubber boots are pretty fragile so I haven't gotten into them yet, but I'm going to have to in order to put my mind at ease about this. My fans work with the AC on, but how exactly did you ground relay #3? Actually how did you ground each relay? I'm just wondering if all the wires are connected to the relay, how do you ground it? Maybe I'm just having a brain fart right now lol. Not much sleep over the last few days.
I love the idea of wiring it so the thermoswitch turns on the fans. I was under the impression that's what they already did.
The thermoswitch does NOT turn on the fans. At least not on my 1994 rx7. The factory wiring diagram and my first hand watching it bears this out. The thermoswitch makes your fans go a little bit faster only if they're already turned on.
test grounding:
I used power probe for testing. Power Probe, Inc.
You don't need for this simple test. I already owned the tool ( i am mechanic ). I love using for electrical work.
For you I would put a paper clip on the back of the relay harness for the wire that is suppose to be the ground. Get a long wire with a clip at each end. Put one clip on a good ground then put the other clip on the paper clip. Fans should kick on.
Some of the wire colors where different than the wiring diagram. So, I would take out each relay first to figure out what is B+, ground, control, etc... It is not hard to figure out, just makes you wonder why the wiring color is different.
I can make video, and take pictures of the wires if you want and tell you what was different on mine. just let me know.
Well that explains why mine still only come on at 206*F though lol. So maybe my system is working like it should.
I'll let you know, but to save you time and trouble I'll see if I can figure it out by your description here. I'm a mechanic too, but not on cars lol, generators, etc for the AF. Thanks!
Very informative thread, I'm in the process of doing a complete rewire of the car and swap to LinkECU G4 Storm so have a couple of questions.
I'm running aftermarket thermo switch of 87/82 and 100/95 and would I be able to ignore the Low speed (yellow) and wire the 82/87 into the medium and the 100/95 into the high ? Would I need to still wire the low up to the 82/87 switch or can it be left un-used ?
I'm running no AC (inc wiring) and will be running aftermarket relays (40amp each).
I think 99% people who install the fc/petti switch don't realize it really does nothing. Yes, I know it turns your fans on from low to med speed but it does NOT turn on your fans sooner. If your fans are already on low going to med does not make much of difference if any. Going from your fan off to low fan is MAJOR difference.
I am seriously thinking about rewiring my fans where the thermo switch turns on the fans ( like how they used to do it ). That way what ever thermo switch you choose will turn ON fans at that temp.
Reviving old thread!
So did you ever end up rewiring this and how do you do it?
Recently replaced radiator with new Fluidyne rad. I don;t think its a related issue however when car is cold and turn on a/c and low fans comes on as it should. However the low speed speed fluctuates on and off. Say on 60 seconds and off for 10 seconds. Should low speed stay on continuously?
so the conclusion from speed junkie, the fc thermo switch dosent turn the fan on at 97c. so dales original post is false ? I'm under the impression that simply shaping out the fd switch to fc switch will alow the fans to turn on at 97c rather than 107c. I'm confused now since I just ordered one for my 94 FD.
Been meaning to put this all in one place for a while. Most of this stuff I've written in bits and pieces in other posts over and over, time to put it all in one place.
The FD has a pair of very good cooling fans to keep temps in check. If they are set up and run properly, you'll have a nice, cool running FD. If njhi daleot, you'll be having problems.
First, a little about the stock fan system.
Fan System Components
- The fans. There are a pair of them (obviously) mounted to the radiator. They are 3 speed fans, there is a resistor built into the fans that drops the input voltage down to change the speed. Both fans always turn at the same speed and they are NOT independant - this is a common misconception. Just think of them as one unit.
- Fan speeds. There are 3 speeds, as stated - Low, Medium, and High. Again, think of the fans as a unit, if they're on low speed, they both turn at low speed, etc.
- Fan speed inputs. This is one area where people get confused. Each input adds up to the fan speed. If you only have 1 fan speed input active (more in a bit on this) you'll get Low. 2 inputs, Medium, 3 inputs, High. It doesn't matter WHICH input, each input in independent.
- Fan relays. These are the 4 relays on the bracket on the passenger side (right side) shock tower. The fan speed inputs trip the relays which send high amp 12v to the fans.
- Fan thermoswitch. This is the coolant temp sensor on the back of the water pump housing under the ECU coolant sensor. It has a one wire connector. This is one of the fan speed inputs. The factory switch operates at 107 deg. Celsius.
- The AC. Whenever the AC button on the dash is pushed on and the AC fans (not the radiator fans) are switched on, this is a fan speed input. Even if the AC doesn't work or is removed, this is an input.
- The ECU. The factory ECU can read the engine's coolant temps from the coolant temp sensor on the back of the water pump housing (the 2-wire sensor with a green plug on the back of the water pump housing). It uses this input as another fan speed input.
- The Electrical Load (ELD) system. The ELD module, which is mounted up above the ECU, receives inputs from various electrical devices on the car (defroster, headlights, etc.) and triggers an output to let the ECU idle up. It is also tapped into the same wire as the fan thermoswitch and can kick the fans up as a fan input.
How the system works stock and the Fan Recall
Stock the fans will not come on until 105 deg. C - this is when the ECU's fan input kicks in. At 107 deg. C the fan thermoswitch kicks on, giving another fan input. Anytime the AC is on, you get a fan input, and when the ELD is triggered by headlights or the like you get another input.
Now, 105 deg. C is HOT. Mazda ran the FD this hot for two reasons - emissions and fuel economy. A hot engine handles emissions better and is more fuel efficient. This was not the best decision from an engineering standpoint, but without it they couldn't have sold the car in the US. That's fine, we can do something about this.
When the FD was still young, Mazda had troubles with the FD running hot and causing engine fires. This was Not Good, so they issued a number of recalls and parts improvements related to this problem. One of the biggies was the Fan Recall. This has 2 components -
- A harness and control box that plugs in by the ECU. The harness goes in between the blue and white connectors to the ECU harness, has a ground wire, and a control box that bolts behind the ECU.
- A harness that plugs in between the fan relays and the front wiring harness. This changes how the relays are wired so they can kick on with the ignition key Off.
The fan recall harness worked by monitoring the fan thermoswitch. If the thermoswitch trips for a certain amount of time while you're driving (I believe 5 minutes or something) it will then remember that it was hot for that length of time and will run the fans for 10 minutes after the car has shut off to cool the engine bay.
While this extra cooling sounds good, remember this was in a VERY hot engine bay with a precat and 100+ degree coolant temps. This was quite hard on the battery and early FD owners reported batteries not lasting terribly long due to the recall.
How to make your fan system better
So, we want to get coolant temps consistently running where they should be and make the fan system happy. This isn't too hard to do.
First, pull the fan recall business. You won't need it. In an FD running SANE coolant temps and with a downpipe instead of a precat, the underhood temps will be nowhere near a stock FD's.
Next, get an FC thermoswitch. This is from the '89-91 RX-7, Ray at Malloy can get you one easily for around $50. It's the exact same as the FD thermoswitch (screws right in, uses the same connector) but kicks on at 97 deg. C which is far more reasonable.
Third, get a PowerFC if you don't have one already. Not only is the PFC one of the best things you can do for an FD, but you can control the ECU's fan speed input. You WILL need a Datalogit to change this. Most guys set it to 85 deg. C which is very comfortable. Mind, the Datalogit shows multiple fan "on" temps - only the first one works on the 93-95 PowerFC, the later ECU's had more fan outputs.
Fourth, if you want to get more hardcore, see if you can find an HKS fan controller. I'm not sure if they're made any more, I have one in my car. It gives full control over 2 fan inputs, I have mine set at 85 deg C and 90 deg. C. The unit is in the same case as their turbo timer, it's easy to wire in and set up, basically set it and forget it. Few FD guys have this, but I really dig it.
To reiterate, you have 4 fan speed inputs - AC, thermoswitch, ECU, and ELD. Each input brings the fan up one speed level. If you are running at 80 deg C and have the AC on, the fans will run at Low. When you hit 85 deg. C with your PowerFC and the AC still on, the fans kick up to Medium. When you hit 97 deg. C with the same 2 inputs active, the thermoswitch kicks on and you have the fans at High.
Could you run the fans at High all the time? Sure. The car will take forever to warm up and use more fuel, the alternator will be loaded down running the fans, and the life of the fan motors will likely be reduced. Your car will also sound like a giant fan all the time. That's a ghetto way to do it, use the fan control system to your advantage.
Can you run an aftermarket fan? Not recommended. Most aftermarket electric fans are pretty lousy - ask any FC guy. They typically don't move as much air, are MUCH louder, draw more amps, and fail prematurely. Mazda really did a nice job on the stock fans and I've yet to see an alternative that's any better. The only drawback to the stock fans are the size, they are a little bulky with some custom setups, but that's about it. They can move a LOT of air.
What about the '99 spec fans? Mazda redesigned the fans in '99 with different fan blades and motors that use less amperage. I've not seen conclusive evidence that they're better than the original fans, but please chime in if you have first hand evidence.
What fails in the fan system? It's generally pretty robust. I have seen bad fan relays before, that's an easy fix. The fans themselves are very hardy, I have seen ones damaged by battery acid and foreign object damage. The wire to the fan thermoswitch connector can break off, causing the thermoswitch to do nothing.
What about the fan switch mod? This is an oldschool mod from back in the day. Before the upgraded fan thermoswitch was discovered and altering fan temps in the PFC was hit upon, FD guys didn't really have a good way to run the fans and keep things cool. The fan switch mod taps into the ECU fan recall harness, you can ground that out to run the fans (it's the same wire as the fan thermoswitch) and then the fans will run after you shut the car off. This is simply not necessary with fans running properly.
That's about it. If you get your fans working for YOU, your FD will run cool and comfortable. Aftermarket radiators, big intercoolers, ducting, etc. are all useless if the fans aren't running like they should be.
hi dale
first of all super thread
but do you know if there a problem or setting on the
apexi power F.C.
since I plugged my power F.C. to my 94 fd3s
i only get one fan to work to speed as it should but the other one works very slow
all was working fine before fitting the ecu after fitting it I noticed the temp on idle raise abit and didn’t hear the fan at speed like I used to so I checked and I noticed that one fan was working faster than the other one
do you know what’s i could be by any chance
or someone had similar issuse
thanx a lot in advance
any help Apprishiated
I also replied to you via PM, but I'll put it here for everyone else -
The fans are a unit as far as the ECU and relays are considered. What happens to one fan should happen to the other one. If one is slow, it's the fan itself or the wiring, that's all it could be.
The ECU (and AC, and fan switch) just trip the relays, the relays send power to the fans. I think it's just coincidence that you are having this issue with the PowerFC.
Does anyone have an idea of what these red wires go to? Could it be part of the fan recall harness? One wire is spliced into one of the fan relays and the other red wire is just dangling disconnected:
And while looking around I also saw this round connector sitting on the frame not connected to anything. Clueless as what this could be??
I believe my cooling fans are only kicking on at high speed for a brief amount of time and not getting med and low speed. I’ve never heard the fan kick on after car was turned off. Troubleshooting and just placed an order for all 4 relays. Thanks for any help with this! Preparing for a hot Arizona summer 🥵
10-14-12, 03:11 AM
