My fan is not coming on when it should (at right eng. temp or when ac is on). The fan motor is fine. The relay is fine. The green/white wire that runs from the relay to the ECM is fine. I understand there is no fan switch in an '86. Whatever tells the ECM to ground the relay is not working. What would that be?

 

bleh, i have a similar problem in my trans am gta '88. my fans also work and so do the relays, but there is no voltage coming to any of the wires on the relay...with the car on or off. they never come on by themselves either, so right now i have a lame *** hookup where i have to pop the hood and plug in a wire from the bat that turns on 1 fan. i need to get that fixed...

 

All I can do now is ground that green wire manually so the fan will run all the time, which is fine, but it's good to have everything working as it should.

 

You could try replacing the coolant temperature sensor. That is what the ECM uses to energize your relay.

 

I'll try it. Shouldn't be too expensive BUT...even if that's the problem, wouldn't the fan still come on with the a/c on?

 

Yes it should. Also, jump the ALDL connector and test like you would for codes. With most ECM controlled fans it should run. Measure the green wire with the AC on or test mode. The green wire should go low and turn on the fan. That wire is driven by the ECM driver circuit. If the green wire is staying at 12 volts either the driver in the ECM is blown or maybe the CTS is bad. Normally a bad CTS will throw a SES light. If you want, ground the green wire with a test jumper. The fan should then run. If it doesn't suspect the relay or the plug for the relay or a loss of power to the relay. I found 2 different wiring schemes for an 86. One shows a sw, the other shows ECM control. Simply start by grounding the green. That narrows it down to only a couple of things.

 

Grounding the green wire does turn the fan on. There is no SES light. SO now what?

 

The coolant sensor might not be accurate due to corrosion? Is that a possibiltity? I don't know for sure but it's like $8 bucks I think and it's not difficult to change. At least you will know that's not the problem.

My fan does not run with the A/C either. I know it's because there isn't enough coolant to engage the pressure switch. Does your A/C blow cold?

Just some more thoughts.

 

Nope, my A/C ain't cold at all. Needs a recharge. Is that why the fan's not engaging with the A/C on?

 

Yep, that's why your fan won't operate with the A/C.