My wife's car has a problem with the primary fan.Basically it won't come on even if the temp gauge gets to the red.I can make the secondary fan kick on by turning the A/C on and and back off and thats what she had been doing but now summers coming and she runs the A/C alot and I don't think the single fan is going to cut it.Ok the fan is Ok,I can get it to come on by grounding the wire to the temp switch in the head or jumping the relay.The relay is good.I changed the temp switch in the pass side head.I checked continuity between the ECU and the relay to make sure the wire wasn't broken and it checked good.Also checked the relay's ground and power connections.Everything seems to check out unless there is something else I am missing.I am begining to think the problem is in the ECU itself.Hoping someone here could help me out 'cause I'm stuck.

 

First thing to do is to replace BOTH relays anyway. They work, then they don't. To determine if the ECM driver is OK use a voltmeter and attach one end to ground the other or positive probe to the wire at the relay coil that goes to the ECM. Usually a grn/wht wire. That line should read 12 volts until the engine comes up to around 225 or so. When the ECM calls for the pri fan that line should then go low energizing the fan relay. If it does and the fan won't run replace the relay and inspect the socket. You can also hold the pri relay in your hand and you will feel it click, if it does and the fan won't run the relay or socket is bad. Or simply swap the pri and aux relays. The heater blower relay is also the same you can use it in a pinch. It's rare to see the ECM driver fail unless someone messed with it and put 12 volts directly to it. The relays and sockets will drive you nut's when they get intermittent.

 

Does any one know where you find the fan relay and where do you shortcut just to see if the fan engine is ok? The car is a -88 GTA...with a very very hot engine..

 

NAPA carries it under thier part # AR-279 or most GM dealers. They run around $15. Not sure with the GTA, my 89 Camaro has the primary one located behind the rad on the cap side fastened with a plastic push fastener. If you locate it you can place a jumper across the 2 heavy guage wires in the connector(orange I think) and the fan should spin up if the motor is OK.

 

Okey guys, I'm new to this electric fan stuff. I just picked up my '88 IROC convt. last week. Love this car.
Which fan is the primary? The fan on the left kicks on when the temp. gets up around 220. When does the fan on the right (aux. fan?) kick on? Does the right one only kick on when the air cond. is turned on? Also, I was looking through a Summit catalog (always a bad idea), any input on the Jet sensor that kicks the fan on at a lower temp. 200 and then shuts off at 185? My last thirdgen was an '83, so I never delt with these fans.

Thanks
Chris

 

Primary fan is on the driver side, aux pass side. Aux turns on at 243 degrees. If you put in a lower aux fan sw you should use a slightly lower stat. Otherwise the fans will constantly cycle. Stock stat is a 195-see what I mean. The other thing is that if you use a lower aux fan switch that truns on the aux fan first BOTH fans will come on. The ECM defaults when it sees the aux on before the primary and then kicks the pri on as well. A 180 stat available at most chain auto parts stores will give you a 5 degree window before the fans run, probably no more than a couple of minutes of sitting at a light before they both will come on. I don't recommend messing with the factory setup because it is engineered for the least amount of wear and tear on the alt, fan motors, relays. It's up to you what you do, you also might look around for an aux switch a little higher than the JET. NAPA has 2 different aux temp switches for the TG's. The stock one, and one a little lower. You might consider that and they are less money-about $19.

 

Thanks Danno. At what temp does the primary fan come on? I checked my aux fan the other night. It comes on with the air on, but does not stay on, kinda cycles on and off. Runs for like 30 seconds. Is this possibly a bad relay?

 

Thats normal, the aux fan is also controlled by pressure in the A/C system. It will cycle as the refrigerant exchanges heat during normal operation.

 

Thanks for the replies. I finally got to do some checking on her car.Here is what I have discovered.Now the primary comes on when the A/C is turned on but the aux. won't.Discovered that I must not have plugged the aux fan back up good.Got that remedied and now the aux will come on but not the primary unless I unplug the aux relay and turn the A/C on.Then the primary will come on and if I plug the aux relay back in both fans will run until you turn the A/C off.Then the primary cuts off and the aux cuts off when it reaches a certian temp.I checked some voltages and found that the wire that goes to the pri. relay from the ECM has 12v on it and then goes low when the A/C is turned on as long as the aux fan or relay is unpluged.With the aux fan or relay plugged up the wire from the ECM to the pri. relay stays at 12v.On the aux relay the wire I believe is coming from the ECM stays low all the time but with it plugged in the aux fan switches on and off like normal.The primary still won't switch on and off with the engine temp. even with the aux relay unpluged.Any Ideas on whats going on would be apreciated.Thanks.

 

Don't forget that the aux also is controlled by A/C line pressure. There is an additional switch that is parallel with the aux fan switch that operates when refrigerant pressure reaches a certain point. ANY time the aux fan operates the primary should also run, what shape is the refigerant charge in?

 

I don't know what shape the refrigerant charge is but the A/c does cool fairly well.My primary doesn't come on with the aux fan at all unless I have the aux fan relay unpluged.Last summer best I can remember everything worked as you described.Over the winter something has went bad.I just can't seem to figure it out what it was.

 

thought i'd get on this band wagon since it seemed pretty active and haven't gotten any responses on my post yet... my problem is that the fans seem to work when they want, but apparently they seem to work. i haven't had a chance to really get in to the troubleshooting of it yet, but looks like i should change both relays anyways. i have a jet fan switch (200/185) on the primary fan and a 195 thermostat. i do have a question about the aux fan, though - where is that switch located? i know it runs off a/c, too, but i didn't know it had a switch somewhere, but i guess that would make sense since it is a back-up to the pri fan. the deal with mine is that although it works, sometimes it doesn't come on when it's supposed to... then next time it gets up to temp, it will work. thanks for any help...

KAM

 

well after going out and troubleshooting... i checked my fans to make sure they did work and i wasn't hearing things, and they did in fact work. before i decided to go and replace the relays, i went back and checked the ground wires on the fender by the battery since i had done some work over in that area before and knew i had them off and low and behold... i left the ground wires for the fans off... silly me so now it should be good to go. i didn't run up the temp so i will check it next time i'm out on the road...

KAM

 

It seems I have fixed the problem.I ended up grounding the temp switch wire which should simulate a properly operating temp.switch and the fan came on.I changed the switch again with one I found at O'rielys auto parts that is supposed to come on at 213degees and now it seems to be working right.I must have put a bad switch in the first time.