Car is a 88 trans am gta and the cooling fans are not working. I know the fans work because I jumped them. The coolant temp sensor is new and I have a hypertech fan temp sensor I am going to install. I also bought a new relay to swap into both relay positions and that didn't solve the problem. I have key on power to the tan wire and power all the time on the orange wire. When I start the car the driver side fan will come on for about 10 secs and stops and doesn't come on again the passenger fan doesn't come on at all. The ac system is not charged so turning the ac on won't do anything for pass. fan. I pulled the harness from the relays to the fans to make sure it was ok as well. Where do I go from here? I think I got power initially to the green w/white strip on initial startup and then it went out after 10 secs or so. I noticed the green wire goes to a large flat plug. From the plug it turns grey and appears to run inside the car. Could this be a bad fan temp sensor for the passenger side fan and a bad ecm for the driver side?

 

Found a diagram while utilizing search, that should fix this problem.

 

Driver side fan is controlled by the ECM. Passener side fan is controlled by the fan temp switch in the passenger side head, between #6 and #8 cylinders just forward of the dip stick.

Charge your AC, you can do it yoruself for under $40.00. It'll work long enough to test the fans. Rurn the AC on. Do the fans turn on?

There are three main components to the cooling fan system. In regards to this, it'll apply to the second fan in your system.



If the fan turns on with the AC, the "circuit" is good and it's one of three things.

1. The Fan itself. You've said you checked so it's not this.

2. On the passenger side of the car between number 6 and 8 cylinders (Just forward of the dipstick) is the fan relay switch. This is the switch that tells the secondary fan when to turn on. Is there a wire connected to it? Mine melted off once causing issues for me. If there is not, that's probably the problem. If there is, disconnect the wire from the switch and, with the key turned to "run" position (not started), ground the wire. The fan should turn on. If the fan turns on, then 90% it's the switch that's bad. If the fan does not turn on, then it's most likely either the Fan Relay or the in-line fuse jsut before the relay. Before moving on to the next test, make sure the wire is still grounded to chassis ground.

3. Another test of the circuit is to remove the relay and jumper the two fat wire leads (should be on the ends). Jumper these leads. This bypasses the Relay itself. Turn key to "run" and jumper the leads or jumper then turn on. Does the fan turn on? Yes, then the circuit is good and the relay is bad or has loose connections. No, then if the fan turned on with the AC in the first step, it's the switch or the wiring between the relay and the switch. --if you turned the AC on and the fan worked, then this will only tell you if the relay is bad or has loose connections. If the fan did not turn on with the AC, then this will tell you that (with the wire from the connector still grounded to chassis ground) the in-line fuse is bad.


Now, there is more involved with the ECM controlled fan, but you can test up to the relay regarding the fan.

The big test is the AC, it'll bypass the circuit and turn both fans on. If you can do this, you'll verify that the relay, fan and in-line fuse are good.

 

There is also a paperclip method you can use on your OBD connector that will bypass the ECm and turn the fan on. Since I have a single fan, it doesn't work for me but if you do a search here on the boards you should be able to find it.

 

I got them working.