Radiator fan motor pinout

[AmirTech]

Hi guys,

I have that problem where my fan motor won't turn on when the car heats up.

Both fans turn on with the AC.

The car:
97 Talon TSI AWD AT
I have:
- changed the temperature sensor.
- tested all the relays and they work fine.
- manually shorted the "Radiator Fan Relay (HI)" and the fan comes up.

The question:
Does anybody know the 4 pin pinout for the radiator fan motor?

I am looking at the wiring diagram and it's a bit difficult to see how the setup actually works.

I do know for my car the following fan operation modes can occur:
Temp. Fan --- AC Fan
Off --- Off
Low -- Off
Low -- Medium
High -- Medium
High -- High

So either the relay is not getting the signal from the ECU, or some connection to the fan is corroded. I'm trying to first figure out the electrical workings of the setup so I know what tests to run.

I appreciate any help. If there is someone in NJ that wants to be paid to figure it out for me...I'm all ears .

This is where I wish I had a warm garage where I could just twiddle with it...20F isn't conducive to me debugging it .

thanks,
Amir

 

[luv2rallye]

Are you sure it isn't due to your new temp sensor? Try shorting the sensor to see if the fan comes on. My '99 schematics for A/T show 2 fan Lo relays (manual has only 1), 1 fan Hi relay, and 2 condensor fan relays (Lo and Hi). On rad fan: pin 2 black goes to ground, pin 1 white/black goes to fan relay L01, pin 3 white/blue goes to fan relay Hi, pin 4 blue/green goes to fan relay L02 which connects it to ground when activated.

 

[AmirTech]

I can't say for sure. I changed the coolant temp sensor because the car was difficult to start when cold. Sometimes, I could sit there cranking 40-50 times to get it to go. The temp sensor wasn't completely dead because the ECU never saw it.

After changing it, the car now starts beautifully every time.

Thanks for the pinouts....I'm wondering how the fan works though?

ECU pin 21 -> Rad (LO1) relay
ECU pin 20 -> Rad (LO2) relay
ECU pin 20 -> Rad (HI) relay
ECU pin 20 -> AC (HI) relay

This is my hypothesis right now...
Rad (LO2) is connected to ground...so it seems like the circuit is:
12V -> Rad (HI) -> Fan -> Rad (LO2) -> Ground

Another is:
12V -> Rad (LO1) -> Fan -> Ground

3rd is:
12V -> AC (HI) -> AC Fan -> Ground

So...pin 20 runs the Rad fan and AC fan.
Pin 21 runs the Rad fan on LO.

I guess this is where I need to understand the functionality of the fan...ie...what of the 4 pins cause what.

thanks,
Amir

 

[luv2rallye]

First of all in this cold weather are you sure the engine gets hot enough to even turn on the fan? You can block the entire radiator off with cardboard and let idle awhile to test.

Each fan has 2 windings, a low speed and a hi speed thus the 4 pins. ECU pin 21 only turns on the rad fan low speed relay L01 by grounding it which provides +12 to the rad fan low winding pin 1 - other side of rad low winding pin 2 is grounded. For the A/T model: ECU pin 20 turns on 3 relays by grounding them. One is the A/C fan hi which provides +12 to the A/C fan hi winding. Another is rad fan hi which provides +12 to the rad fan hi winding pin 3. The third is rad fan L02 which connects the other side of the rad fan hi winding pin 4 to ground. I don't know why they didn't just eliminate L02 and connect the other side of the rad fan hi winding pin 4 to ground like they did in the M/T model (it might have something to do with the N/T model which uses L02).

 

[AmirTech]

luv2rallye,

Thank you very much for the comprehensive analysis . I have seen lots of people with this problem with no clear way to tell what to test. I hope this helps other people as well.

Yes, I tested the car by forcing it to overheat by just sitting there...I tried this is warmer weather and my temp guage goes to about 3/4 without turning on. My idle starts to suffer with the higher temp and my low oil light comes on (sometimes). I believe all symptoms of running too hot.

I'll test my LO1 circuit and see if it's working. I'll post up results once I figure it out.

thanks,
Amir

 

[AmirTech]

I went outside to test the car out...weather is good so good time to do it..

Okay...after much fiddling around with everything...

Here is what I found..
- Rad (LO2) is labeled Rad (HI) along with the other Rad (HI)..kinda weird.

- all the relays work -> I tested them by using keeping the AC one which periodically turns on AC (LO) and Rad (LO1). I switched relays on those two just to make sure things work.

- 12V are coming across all terminals that power then. Only Rad (LO2) has ground on it (as expected).

The problem...

I found the Rad (HI), Rad (LO2), and AC (HI) control signals to the relay both set to 12V on both sides of the relay. One should be 12V coming from the ignition which is correct. The one coming from pin 20 should be ground (or float). I tested the voltage relative to the battery ground and saw 12v on both sides of all three.

The control signal on 21 seems to be working correctly. I believe when the car heats up, the car only turns on pin 21 to cool the car down.

There is a SuperAFC installed on my car that was done by the previous owner...I wonder if they screwed something up during the install.

Anyhow..this is where I am...if anybody has seen anything similar....shoot me a reply .

thanks,
Amir

 

[luv2rallye]

Yes pin 21 is the normal fan on (L01). The other side of the relays float until the ECU grounds them (to turn on the fans) so they will read +12v (thru the relay) when not on. Pin 20 goes low to turn both fans on hi when ECU detects engine extremely overheating.

 

[AmirTech]

I tested it again and my car definitely overheats...

So if the AC is off...and I'm sitting idling...then when the car begins to overheat:

Does the car use pin 21 (ie. Rad (LO1)) to cool the car down??

OR

Does it use pin 20 (ie. Rad (HI) & AC(HI)) to cool the car down??

I believe that it uses pin 20 at this point to cool the car down which is the pin that isn't working which is why the car overheats. I'm just surprised how my pin 20 can be tied high . If it was just open, that would make more sense.

I'm going to check at the ECU and see if the continuity between the pin and the fuse relay is good.

Also, another weird thing I saw is even though the Fan (LO2) is open, I can short the Fan (HI) and it the fan runs....this means that the Fan (LO2) is being ignored for GROUND.

thanks,
Amir