Boost Lee

iTrader: (3)

Yeah, I waited the 150 seconds... no luck. I'm gonna try and find another FCM

adam c

iTrader: (2)

I have this same mod on my car, and use it frequently. Its especially helpful after a hot autocross run: I'll let it idle for a minute or two, then turn off the engine with the fans still on. After a minute or two, I'll start the car. The coolant in the radiator will be much cooler since the fans have been running, and it will cool the engine much more quickly.

KevinK2

I agree. Adam, I go back to the "big list" forum, and I think I remember you back then as a "pioneer" in the understanding of the way the FD runs.

On my old Saab Turbo 900, I ran a test for turbo cool down, trying engine running on like a turbo timer, and rad cooling fan run on, the we get on the FD's with the "fan-mod". I measured the hot turbine hsg with a Themocouple that was designed to be placed under a spark plug hole, that I put under a center section bolt on the hot side.

The difference was big, the air passing over the stopped engine made the turbo much cooler vs the engine run on, continuing to creat heat. Now this was just an oil cooled turbo.

KevinK2

Cooling Fan Recall Thread:

https://www.rx7club.com/3rd-generati...cation-385773/

More info

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KevinK2

My 2006 input:

https://www.rx7club.com/3rd-generati...sensor-505812/

sounds like just the loads can turn fans on at 210F, likely an ecm control with load input.

KevinK2

Ok, upon closer inspection, my 93 diagram from the 93 Wiring Manual, is the exact same as your 94 diagram from the 94 Wiring Manual on page 1, both don't have the FCM.

I have a copy of another 93 diagram that includes the FCM.

The 93 Service Highlights has the conditional table, and a wiring diagram without the FCM.

The best wiring diagram, from my "recall" link above:





And the Related Table:

https://www.rx7club.com/attachments/...tion-small-pdf

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KevinK2

Fan Control TSB

The Fan Control update Service Bulletin was about 10 pages for installation, including a sketches. I copied by hand the steps to check out the installation:

1) check batt

2) ign on -- no fan

3) ign off -- no fan

4) gnd test wire from FCM

5) ign on, aft 150 sec, fan on
6) ign off, wait 20 sec, fan stays on

7) disc't connection at fan relay A, fans spd lowers

8) reconnect connection, fan spd increases

9) disc test wire at FCM, fan spd lowers

10) ign on, wait 15 sec, fan stops 8-12 sec after ign on

11) ign off, test done

Notes:

A) pre Apr 1 93, P0210660, fan operates by ign on

B) after Apr 1 93, P0210661, fan operates 100-150 sec after ign on

C) wait for 150 sec after ign on for both groups

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Boost Lee

iTrader: (3)

Yeah

If the FCM is meant to turn on the fans 150 sec after ign on with test gnd. Mine is bad. I'll need to find another.

Kevin, we may have come to the conclusion of why so many people have made the statement that the thermoswitch doesn't turn on the fans. There are probably 93 cars that don't have the Fan recall, correct? And without the FCM, the fans won't get turned on.

Thanks for joining in the hunt!!!

KevinK2

I do feel bad about how I thought you were wrong many times, when it was due to looking at 2 different diagrams.
Next time I have my 93 out, I'll do some testing.

I read some place that the motor speed is varied by resistors inside?
Looking at the motor, there are 4 connections:

C) permanent gnd.

D) gnd from Relay#3, IF coil grounded by temp-switch, FCM, or test wire off FCM

B) B+ IF fan relays are grounded by FCM or ECM
[ "B" terminal is the only one that gets a signal from the Load Module. ]

A) B+ if AC used.


Based on the wiring diagram above (same as the one on post#5), it's possible that "D" terminal (needs a gnd) is dedicated to T2, based on the fan-switch only.

So I think the 3 active terminals at the motor are related to the 3 speeds.

Also think a Load signal is the same, if it has just the headlights or all 3 loads shown.

Using the FC switch will void the 221F ecm trigger for fans on low. But, low speed still is possible if the AC is on, or if there is a load signal.

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Boost Lee

iTrader: (3)

Yeah, I kept thinking, "This dood is speaking really logically, he's gotta be reading something different from me. I wanna read it too and see if I end up with a different perspective"

What's T2 that you keep referring to?

Kevin: Also think a Load signal is the same, if it has just the headlights or all 3 loads shown.

Response: Yep, on any or all of those 3 inputs the electrical load logic causes the ecu to trigger relay #2 and #4 with just 1 speed input.

Kevin: Using the FC switch will void the 221F ecm trigger for fans on low. But, low speed still is possible if the AC is on, or if there is a load signal.

Response: Yeah, the FC switch only increases fan speed. When it's triggered, the FCM turns on the fans via relay #2 & #4....resulting in medium speed as the slowest speed (without A/C involved).

KevinK2

T2 means Temperature #2, ( Engineering Abreviation)
For OEM:
T1 = 221F
T2 = 226F

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Boost Lee

iTrader: (3)

Yeah, terminal D on the fans is switchable only by input from the thermoswitch.

KevinK2

I remember why I did not bother with the FC switch. I read about, and verified in 2006 that for my 93 FD, I could have a low speed set point at ~210F by leaving the parking lights on, or by leaving the fans on at speed 3 or 4. I think this is related to motor terminal B.

https://www.rx7club.com/3rd-generati...2/#post5264632

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Boost Lee

iTrader: (3)

Yes, the ecu turns on the fans at a lower temp than 221 when the EL Load active, but I don't want to play an active role in turning my fans on and off. I just want them to come online at a lower temp, leaving me to just drive and enjoy the car.

adam c

iTrader: (2)

The FC thermoswitch is not difficult to install. Just a little tight to get in there ............. like everything else on the car.

Call Ray Crowe at Malloy Mazda. Part number is PN41-18-840

KevinK2

With all the sealed ducting I have up front from race prep, including the Peter Farrel big duct for cooling air for just the ported Greddy SMIC, and my sepatate cool air duct for the intake, and fans-on when AC is used, I rarely had to use a load to get fans on, as temp was mostly below 210F.

To really understand how the system works, it would be helpful to test the motor terminals, engine hot and cold, to see if resistors are used to alter speeds. You could also check the PFC-ecu and how it is used with the fans for more "data".

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KevinK2

If it were me with that goal of all automatic, I would want the fans to come on at first at low speed at 210F. Nascar runs engines at 240F by design, to reduce the amount of wasted heat energy, so I'd stay with the stock T-stat, especially for DD in cold climates (starts opening at 180F, fully open 203F). The mid speed would come on at 215 to 220F, and high at 226F(AC on).

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Boost Lee

iTrader: (3)

Can you do me a favor a put up pics of your ducting for the radiator? I'd like to see the detail on the extra stuff you've done. From what I could tell the factory undertray looks like it should do a pretty good job, but my car does end up running a bit warmer than I want and ends up in the 200-210 degree range way too frequently for me to be comfortable.

KevinK2

I'll try some pic's. Air entering the "front mouth" MUST go through the rad or the IC. I made sealing pieces from a sheet of rubber, that seal on the sides between the radiator and the undertray. For charge air, I used the empty right oil cooler duct (touring model has just the left side oil cooler) and created a separate source around a smaller coolant expansion tank. I also have the Ron Davis Race Radiator, about 1-1/2" thk. This was a mostly tracked car.

Are you completly stock?

2slo4my7

iTrader: (3)

Nothing wrong with regular temps of 200-210F. Above 220F is a bit high.

Mazderati

iTrader: (3)

For those not so adept at reading wiring diagrams, is there consensus that the FC fan switch does not turn the fans on earlier (or at a lower temperature) than the FD switch, but instead turns the fans on at the same time (and same temperature) albeit at a higher fan speed?

Boost Lee

iTrader: (3)

I need to find another Fan Controller to be willing to totally recall my statements.

wstrohm

Each fan motor contains a low-speed circuit (the A-C winding in the schematic above) and a medium-speed circuit (the B-D winding). So there are three possible states (besides "off"): A-C conducting current gives low speed; B-D conducting current gives medium speed, and both A-C and B-D conducting current gives high speed. Both fans are controlled as a single circuit, although each has its own relay because of the high currents used by the fan motors.

The FC fan switch ("Engine Coolant Temperature Switch" in the schematic above) closes Fan Relay #3's coil at 207°F instead of 221°F like the FD switch. Fan Relay #3 responds by connecting the "cold sides" (Terminals D) of the fan motors to ground. This is an "enabling" circuit for the medium-speed fan coils "B-D."

Medium speed cannot run unless Terminal D is grounded. But in order to run at medium speed, Terminal B, the power supply to the fan motor's medium speed winding must also be at +12 volts.

With Fan Mod Installed

If you have the Fan Mod, power to the "hot" side of the fan motors' medium speed windings is controlled by Terminal E of the Fan Control Module, which in turn is controlled by the Fan Switch driving the FCM's Terminal C. When the Fan Switch closes, it pulls the FCM's terminal C to ground. That also pulls terminal E of the Fan Control Module to ground. The two relays connected to Terminal B of the fan motors then close and power the medium speed fan motor windings, which fires up the fans at medium speed if the Fan Switch is closed. Therefore, with the Fan Mod installed, medium speed of the fans will be turned on if the Fan switch closes... at 207°F with the FC switch, or at 221°F with the FD switch. (Note that the ECM is "wire-OR'ed" with the Fan Switch at Terminal E of the FCM; this means that the ECM can keep the fans running even if the Fan Switch is open. This is how the fans can run after the ignition is turned off.)

OEM Fan Control (No Fan Mod)

Without the Fan Mod, the Fan Control Module does not exist. The fans cannot run after ignition is turned off. The schematic for that case (from the 1994 FD Workshop Manual, page B-2) is attached below. (Info below also required looking at page B1-b to determine ECM terminal 3D was the control for power to the fans.)

For this case, the Fan Switch ("Water Thermoswitch (Fan)" in the attached schematic) directly controls "Coolant Fan Relay #3." Open, the "D" terminals of the medium speed fan motor windings are open, and no current can flow in those. Closed, and those motor windings are at ground (enabled) through Relay #3. Power (+12 volts) to the "B" terminals of the medium speed fan motor coils is provided by fan relays #2 and #4 only when terminal 3D of the ECM (PCME) goes low, which is controlled by the water temperature sensor circuit.

So in this case, the engine computer determines, if the Fan Switch is closed, whether the coolant temperature demands the medium speed fan needs to be active. Note that in this case, if the Fan Switch is open, even if ECM terminal 3D goes low, medium fan speed is disabled and only the low speed can run.

wstrohm

Sorry no OEM schematic was attached; problems with H-P scanner software running under Mac OS X 10.9.4. Working the problem... meanwhile it was only going to be a scan of the manual page anyway.

KevinK2

Excellent Job! Now can you create a simple table for the circuit with the FCM, or just link to one already posted if consistent with your thoughts.

Are you sure that in your 1st section, you are correvt to say the FD fan switch turns the fans on at 221F, vs 226F ?

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