Got an 85 Camaro with the stock single electric fan setup.

The problem is that somewhere in the harness, a PO jury rigged it to bypass the ECM and the fan is on 24/7 as long as the engine is running. I wanted to reverse this and revert back to the stock ECM controlled setup since I don't want the extra draw on the alternator unless needed.

Now here is where I get confused. I read that the fan relay is supped to be up by the other relays on the firewall. mine is mounted at the front of the engine bay right next the battery and radiator. Is this correct?

Also, the part that I really don't understand. The fan on/off temperature is monitored and controlled by the ECM. I am running a custom chip so I can dial in any temps I want however if the ECM monitors the temp through the CTS then what is the need for that fan switch that goes in the passenger side head which BTW I do not have and there is no trace of the single terminal harness that would have gone to it.

 

In my service manual (1990) the VIN E V8 cars don't have ECM control of their single fan, a temp switch or having the A/C on runs the fan.

On the VIN F or VIN 8 V8 cars, they have dual fans. The ECM controls the primary fan. The fail-safe switch in the head or having high A/C head pressure runs the second fan.

 

Single Fan set ups have a fan relay, by the firewall. There are two identical looking relays, one for the fuel pump and one for the fan. I am pretty sure the fan has only 4 wires to it, a search on the site here will tell you.

Your fan is NOT ECM controlled. There is a fan switch on the passenger side head, just between the #4 and #6 cylinder. This is pre-set factory and makes the fan come on at 225*. It turns off at 200*. There is one wire that goes to it from the relay on the firewall. The fan is also programmed to come on with the AC being switched on.

the ECM only controlls the primary fan on dual fan set up's.

If the factory plug is near the fan, you sould be able to trace the plug/wires up along the drivers side fender to the relay.

If your relay is in the fender by the battery, it's probably because they bypassed the factory set up because it wasn't working for some reason. If you could post a pic of how it's set up, that would greatly help.

 

Sorry, but this is incorrect.

I spent hours last night trying to trace down the problem. Everything was setup exactly as the factory designed it. The problem was the ECM would not release ground on the green/white wire that goes to the ground side of the relay coil. It turns out, there is a two wire connector that went to a switch in the A/C hardlines that kicks the fan on via ECM when the A/C is turned on. Since a PO removed the A/C from my car the harness was not hooked up to anything leaving trying circuit open and making the ECM think A/C was being requested all the time.

85 was a weird and unique year for TPI. I all but tore my hair out trying to sort out the problem.

 

The ECM in a single fan set up has zero bearing on the temp the fan comes on, so if it controlls it when the AC comes on, that's news to me, because on my 84 single fan set up, turning on the ac energizes another wire on my relay which turns the fan on.

 

Something similar on my '87 2.8L.. Brought the car brand new, and the fan always ran as soon as the engine was started. I didn't think it was a problem 'til one day I happened to unplug the A/C pressure switch and I noticed both prongs of the plug had been bent over inside the plug, so they never made contact with the switch! I don't know if this was done by accident on the assembly line, or my theory that the dealership did it to maybe prevent the buyer from complaining that the fan did come on soon enough (???)... Anyway, I was able to restore the prongs without breaking them. Now til this day the fan only comes on when the A/C is on, or when the engine temp gets really hot if the car is idling in traffic for a long time.