My '94 9C1 - radiator fan does not start in time, engine overheating

[ayrat]

Engine overheating, symptoms:

Temperarature gage is reaching red line and that's when one the two radiator fans starts. This gives a little drop in the temp but apparently not sufficient, as i start smellig burned metal when engine is too hot. The second one does not kick in.
But when I turn AC ON both fans start working and temp drops down to the normal middle of the gage whithin couple of minutes, thus providing sufficient cooling. So obviously fan relays, fan motors, coolant level and clogged radiator are not issues. Also tested the coolant temp. sensor with Ohmmeter at differnt temperatures as described in Hanes manual. Got perfect readings as in the book. The oil temp. sending unit is not connected to PCM but only to the gage according to the wiring diagrams and i think it gives correct temp. readings.
Did anyone had have this problems? Could it be something wrong with PCM program? Got this car through auction from county police, and i read somwhere they might reprogram PCMs before selling to the public...

[PeteA216]

It is a possibility that your pcm is the problem, but try replacing the temperature sensor first.

[JoeinLA]

Originally Posted by ayrat

Engine overheating, symptoms:

Temperarature gage is reaching red line and that's when one the two radiator fans starts. This gives a little drop in the temp but apparently not sufficient, as i start smellig burned metal when engine is too hot. The second one does not kick in.
But when I turn AC ON both fans start working and temp drops down to the normal middle of the gage whithin couple of minutes, thus providing sufficient cooling. So obviously fan relays, fan motors, coolant level and clogged radiator are not issues. Also tested the coolant temp. sensor with Ohmmeter at differnt temperatures as described in Hanes manual. Got perfect readings as in the book. The oil temp. sending unit is not connected to PCM but only to the gage according to the wiring diagrams and i think it gives correct temp. readings.
Did anyone had have this problems? Could it be something wrong with PCM program? Got this car through auction from county police, and i read somwhere they might reprogram PCMs before selling to the public...

I had the same problem with my 94 9C1 (LAPD Highway Interceptor)
The 94-96 9C1 had a faulty design and all were overheating originally.
you have to take it to a GM dealer, they have a replacement-kit and instructions from GM what to do. You can also buy only the kit, but the job is complicated. Normally the gauge should barely be above the 0-mark when cruising, without any AC on.

['97ventureowner]

JoeinLA, please read the Community Guidelines. This is the 3 rd thread (so far) that you've brought up that has been inactive for a long time. Continuing to do this can lead to a temporary ban on your account privileges.