Ever since I got my 1991 Firebird the stock radiator fan control didn't work, the previous owner installed an aftermarket relay and wired the fan to that. Well the system that they had installed recently went out, so now I'm trying to make the stock system work again, and here are my findings.

Just to clarify, I have not reconnected the fan to the wire that is supposed to give it power, (black with a red stripe) I have tested to see if it gets 12 volts, and it does not. Anyway, I took a DMM to the connector for the relay and here's what I found;

Green wire: Car was run until reaching 220° and even then this wire only put out 0.1 Volts
Brown wire: ~12v
Red wire: nothing.


I also tested the wires on the coolant temp sensor with key on, engine off and here's what I got;

Yellow wire: ~3 Volts with connector on sensor, 5 Volts with it disconnected.
Black wire: 0.1 Volts

Any help on this issue would be appreciated, thank you.

 

Go to the How -Tos section above or here,
https://www.thirdgen.org/technical-articles/
then down to the electrical section and then click on the stock fan set up you would have in your car. That should give you plenty of info to start seeing what you have to deal with

 

OOPS, meant to add that if possible get info on system installed now if there is a product name on it or anything. Might well be an improvement over stock system. Your choice

 

I'm not entirely sure how helpful that article will be, because it says "There is no ECM control for the fan on single fan applications." Which is inaccurate because 1991s with single fan setups do in fact use the ECM to control it, and I think the problem might directly involve that and something somewhere with the red wire, because in diagrams that wire is labeled "hot at all times" and it's not getting power.

 

What is the other end of the red wire attached to?

 

The wiring diagram I looked at shows it going to a fusible link and says "always hot," however, it does not show where it goes from there.

 

not meaning what the diagram shows, where is the actual wire that you say has no power connected to

 

As simple as the question seems, maybe I'm misunderstanding it

The red wire is between the brown wire and the green wire on the connector. Having a hard time trying to trace the wire back to where it starts.

Edit: just re-read your question. I think it might go to the battery or alternator, but I'm not sure.

 

Exactly which connector are you referring to? And what makes you think the single fan is actuated by the ECM?

 

I'm referring to the connector for the radiator fan relay (connected to a metal structure with 2 other relays that sits up against the firewall on the drivers' side.)
I have read in several places that single fan setups on 91s are controlled by the ECM, and that the green wire w/ a white stripe is shown as going to the ECM in the diagram, I also used my DMM to do a continuity test on it from the ECM to the relay connector and it turned out okay.

 

On the stock fan relay connector there are four wires. The red wire supplies the power to the relay that is sent back down the red and black wire to the fan when the relay is actuated. The little brown wire is hot with key on and the green with white stripe wire is grounded where it connects to the fan switch
which is the action that makes the relay transfer the power to the fan. No ECM involvement whatsoever. The weak point is the often failing fan switch that inspires many to use an alternate relay system using a sensor in the radiator
fins or in the stock fan switch location. In the how-to section there is an article about making a better fan control that will explain more if you read it. Have fun