Ok....it's a 1987 GTA. 5.7 TPI auto. Dual electric fans.


Originally I had an issue with the fans not coming on. Found the fusible link with a burnt wire so I bypassed the fusible link and installed my own fuses.



While doing that I somehow wired the fans to come on as soon as the engine starts no matter how hot or cold the engine is. This is Miami so it's blazing hot most of the time so this was an unintended bonus.



Great so now the fans stay on and the engine is cool.....until I turn on the A/C....the fans turn off when I turn the A/C on which of course is no good. But it doesn't happen instantly....the fans will run with the AC on for between 5 and 10 minutes before they cut off. The car can be sitting in the driveway running with the hood open or being driven on the road. Turn off the AC and fans come on instantly.



Can someone tell me where the wire is that links the A/C with the fans so I can cut that sucker out! LOL


I want FANS ON WHEN ENGINE RUNNING AT ALL TIMES A/C OR NOT!


I am super close to ripping the factory fans out and getting some after market fans with the damn on/off switch on the dash. But I prefer not if I can get around this issue.

 

Well not sure how replacing a fusible link would result in that! So the two fans have separate relay to control each one. The Main is controlled by the CPU and the aux fan is on by either the aux fan temp switch or the AC pressure switch.

Although I don't condone this behavior, if you ground the Dark Green/White(make sure your colors match this schematic) from each relay plug they will turn on as soon as the key is in run.

I feel like there is more to this story though in order to get them to act this way since there is a degree of separation between the two circuits.

 

Here Ya' go; (from the 87 Shop manual,.......)







First and foremost; Your fans are apparently NOT wired as these diagrams show. The ECM should only be in control of 1 fan. The green/white wire is the 'switched ground' wire to each relay that turns each fan ON. (1 green/white from the ECM to 1 relay, and 1 green/white from the head sensor to the other relay. )

The Blue wire is the 'switched ground' AC pressure switch to the ECM.

 

Thanks let me dig into it a bit. This helps.


And yeah I highly doubt the fans are wired from factory. It's a 30+ year old car and I am certain the engine has been out of the car and rebuilt....it runs WAY to good for a 120K mile car. Plus anyone with the trained eye can tell if an engine has been out or not.



The car came from up north so I think they removed the AC or at least disconnected it from the electrical system. Then the car made it to Miami, FL and someone got the AC going again. I found the pressure switch on the compressor jumped..meaning compressor would NOT shut off in the event of a high pressure situation......which is how I found this problem. Fans shut off and AC started making lots of noise and actually blew some refrigerant out of the compressor (looked like a NOS blast).



AC still works so I guess there is a pressure relief valve on the compressor someplace. I see no evidence of the compressor leaking and the AC still blows nice and cold.



Question...the temp sensor on the head....is that just for the temp gauge in the dash or would that have any effect on the cooling fans?

 

Found something.....found "it" I think. My car has two fan relay's in the front right of the engine bay, down by the headlight motor. Just to test with the car on and both fans running I unplugged each relay one at a time and the corresponding fan shut off.



Someone jumped the green/white wires between the relay's.



Meaning.....no matter what..one fan comes on then both come on. One fan goes off then both go off. Still not sure why either fan would shut off when the AC turns on.....but by cutting the jumper they put between the green/white on each relay and grounding the green/white from each relay individually....the problem seems to be gone. At least with my tests in the driveway. But the fans would always shut off even sitting in the driveway after only a few mins of having the AC on.


So now with my temp ground jumpers....the fans stay on. Time to take it for a test drive. It's hot as hell and about to rain so AC is a must right now!

 

Drove the car yesterday. Put 20 or so miles both highway and city driving and problem is gone. Thanks for the help!