I've got a very weird problem with my dual fan setup. If I do not turn on the A/C, the primary fan does not click on at all. However, if I kick on my A/C, both fans come on and run normally. When I kick off the A/C, the primary fan stays on constantly, regardless of the temperature. All the relays are good, as the fans will kick on normally, and I even changed the relays just to be sure. The Coolant temperature sensor underneath the throttle body is new as well. Could this be a problem with my ECM, or is there another component I'm missing?

 

TTT
anyone? It's 120 here and my car doesn't like it

 

please help, doesn't anyone have any ideas? Is this a severe electrical problem, or does the A/C have some sort of control over the fans that might be causing this?

 

I'm not sure if this a related problem, but perhaps the A/C has control override on the fans, but today, I had my vents on, and when I shut down the car, the vent fan stayed on after the car was off. I turned the AC fan control to off and the vent shut off. Cound there be a relation between these two problems?

 

AC request calls for both fans after the pressure switch operates. The primary fan is controlled by the ECM, but if it is coming on with air on you can rule out the computer since the ECM driver turns on the primary relay. What does the temp guage say when the pri fan does not come on, it should come on at 220-225 degrees. A simple test of the ECM and circuitry can be done during code retrieval. Jump the ALDL connector as if you are going to test for codes, during the code retrieval process the pri fan will come on as a self test as the codes come up. That rules out the ECM, fan relay and associated circuitry. You must wait until the guage goes over the 220 mark normally BEFORE the pri fan will run. With 120 deg ambient temp its probably normal for the pri fan to run, but it should shut off after the temp guage gets to around 190 or so. If it does not shut off after the air is turned off(it is normal for the pri fan to run a short time after the AC is turned off) suspect the AC pressure switch. The aux fan switch and AC pressure switch internally ground the aux relay, but anytime the aux relay is grounded before the pri fan reaches it's turn on temp the ECM defaults and turns them both on. As far as the blower or vent fan suspect the blower relay, they can have burnt contacts and they sort of weld shut. Also the control head can have a problem, seen many burnt switches in them also.

 

Thank you so much for your reply danno! THe primary fan comes on with the ALDL jumped, but does not come on at any temp (It redlined before I rejumped the relay to force it on. AS for the A/C relay, I checked it, and it's working fine. Now, onto the pressure switch and the control head. The only problem is I have no clue where to look. I feel dumb, but I don't know whre they are located. I'll keep on it and see what I can find, but any more help is greatly appreciated.

 

Anyone? I know this has to be a simple answer, yet I cannot find anything about it when I search the forums. Can anyone help?

 

First, it should not redline because the aux fan sw should turn on BOTH fans at 238. The aux fan sw is not controlled by the ECU at all. It is a sw that grounds the aux fan relay and it also sends a signal to the ECM to tell it to turn on the pri fan if it is not already on. The aux fan sw is on the pass side block between cyls 6&8. Don't confuse it with the knock sensor. Y should be able to ground the wire on the aux fan sw with the key on engine off and the aux fan should come on and the pri will also kick on after a brief time. Do Y have a coolant pressure problem or leak or low coolant level? Y have another issue here most likely not related to the electronics.

 

My coolant level seems to be fine. I had to replace my water pump a few weeks ago, but this problem existed long before that, adn still continues even with the new water pump. I know where the secondary fan switch was, I replaced that as well in my quest to get this fixed, and it does come on fine. The primary fan in my main problem now. It still will not activate on its own, only if I hit the A/C, then it won't shut off, even after the temperature dropped below the line it should. I will check the pressure on my cap, to be sure I don't have a pressure problem, but flow and coolant levels are fine. THanks again for your replies Danno, I really do appreciate it.

 

Sounds like your temp sensor is bad.