Hello,

First off we're talking about a 91 rs with a 305 TBI with a single cooling fan.

I decided to go ahead and do the remote fan turn on by taking the wire from the fanswitch that is located by the 3rd spark plug on the passenger side and running a pigtail wire from it to a switch in the dash. Then I ran another wire to a ground on the body of the car. (everything worked fine at this point)......

Here's where I F'd up!!!
This is a lighted switch and I wanted the light to come on when the switch was on. Thinking it only needed a power source for the light.... I took a wire from the fan fuse and ran it to the 3rd terminal on the switch in the dash.
I turned the key to the run position and flipped the switch on. The fan motor came on and the little light in the switch came on. And immediately afterwards everything went up in smoke and lots of it.

I turned everything off within a matter of seconds.

It fried the wire going to the fan fuse and the wire going to the body ground, but NOT the wire going to the engine fanswitch.

I disconnected everything and checked to see if the fan would come on with the A/C on. I did not, and it did before I added this remote turn on switch.

I checked everything under the hood for the cooling system.

The fuseable link is fine, the relay is fine and the fanswitch is fine but I'm not getting power to the fan motor.

Here's what I've troubleshooted to this point.

Using an ohm meter.....
The plug that connects to the fan motor. I put one of the leads in the - side of the plug and the other lead to the body. I got a reading so everything is fine?

I put the lead into the + side of the plug and the other lead into the same wire point on the relay and got a reading. This tells me the wire (black with red stripe) is not fried from the relay to the fan motor.

I plugged that wire back into the fan motor and then jumped a wire at the relay from the hot wire to the hot wire for the fan motor.
The fan came ON! This tells me that I'm getting juice from the battery I have a ground to the fan and the wire to power the fan is fine.

I also tested the relay and it worked fine as well.

At the relay there are two other wires which are green/white and brown.

I turn the key over to run with A/C on and used a volt meter to see if I could get a reading from these two wires.
I did get a reading but one was stronger than the other.

So now I go and check the fuse again. I looked for burnt wires ontop of the fuseblock and there are no burnt wires.
The fuse is fine and I even put in a new one to make sure.
Still no dice.

Where is the problem at?
I'm pretty sure that the problem has to be inside the car and not under the hood.
I checked each wire that supports the cooling fan and they all gave me a reading with the meter.

Any clues?

Right now I'm using the switch to power the fan direct from the battery by using the relay wires as my source.
I'd like to get it back to the way it was so that the fan will come on when the A/C is on.

Thanks for any and all ideas you may have.

 

I've got to say, that is one incredibly detailed post

The green/white wire should be the controlled ground by the ECM. At the relay with the key in the 'run' position (but not running), you should be able to ground the green/white wire & the relay should click kicking on the fan. If it doesn't there's no +12 source getting to it.

The brown (or tan w/white stripe on dual fans) wire should be the 12+ switched ignition for the relay. There may be a chance this wire got cooked somewhere along the line.

The A/C should only make the ECM request the fan if the car is running. All switch/sensors that make the fan kick on only switch to a ground.


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