I have a 91 camaro RS 3.1... my cooling fan is not turning on when it reaches the proper temp. When I ground the diagnostic terminal the fan turns on... I know the relay is good... I have not tried turning on the a/c yet ( just read some posts tonight) all the wiring apears to be good (shows coninuity)... this started when I over heated one time.. the fan used to run when I bought it for a couple weeks... I am getting a temp reading on the guage could the sensor not turn on the fan but still give me a temp reading? thnks for the help...

if possible please send posts to

soulblade@core.com
Thanks in Advance
Raymond

 

I believe that the ECM turns on your fan when coolant temperature reaches a certain level determined by the CTS (Coolant Temperature Sensor) located near the upper radiator hose on the intake manifold.

With the car running (at any temperature) disconnect the two wire connector to the CTS and see if the fan comes on. Or remove it and then re-connect it (I can't remember how I got it to work for me [see below]). If so, then the problem would point to the CTS.

I had the same problem when I had a V6 '92 Camaro - temperature ran high as noted on the gauge (sensed by another sensor) because the fan suddenly stopped working. I correctly figured the problem to be the CTS because disconnecting the connector for the CTS would turn the fan on. I can't remember just exactly what I did; leaving it disconnected would not have it "on" every time the car was started, or it would "time out" and eventually stop when the car was running - I can't remember exactly.

EDIT:
Of course, replacing the CTS solved the problem.

[This message has been edited by Stuart Moss (edited June 27, 2001).]

 

Yes if you disconnect the Temp sensor it will run the fan NON STOP till it gets a signal back from the sensor, (it's a fail save mode) it should also set a code when you unplug the sensor, code 15 or 14 I think, if it does not set a code when you unplug the sensor and start the car with out it, that means the ECM has a bad circuit and needs replacing. BUT IF IT DOES then the temp sensor is bad and just replace that, it's only $10 bucks

 

Yes the gauge has a different sensor which is behind the A/C compressor on the drivers side head.