cooling fans not coming on

[denmarjs]

I have a 2000 grand prix 3.1 the cooling fans do not come on even when I`m in the red.Now my ac does come on either (ac clutch does kick on)Had to replace cannister on ac wiring wore a hole in it.My question is will the cooling fans come on even if my ac isn`t charged.I checked all fuses,relays.diode.Is there a cooling fan temp sensor?Any help would be appreciated

[BNaylor]

The PCM module uses the A/C hi/lo pressure switch to turn on the cooling fans in conjunction with monitoring engine temperature through the engine coolant temperature sensor (ECT). So if the A/C system is not charged the cooling fans may not turn on when the A/C is on. The fans should turn on in low speed at around 225 degrees and hi-speed at 230 degrees. The same ECT sensor is also used to display engine temperature on the IP gauge.

If you are in the red zone then find the cause for the overheating. Could be a bad thermostat, LIM gaskets, or the cooling system needs a flush and new coolant.

A simple test is to disconnect the ECT sensor and see if the fans turn on. With engine off remove the electrical connector to the ECT located by the thermostat on left side of engine. Then start engine. Fans should turn on in about 5 seconds. That way you can see if the ECT is the cause, wiring, PCM module or cooling fan control relays, etc.

[denmarjs]

Well I did the test you said to do and the fans do come on.But my a/c clutch does`nt go on when a/c is put on ( do not have a/c charged) will this cause the problem or is the PCM done.

[BNaylor]

In order for the fans to turn on at the proper temp or with A/C on (enagage compressor) the system must be properly charged. I would look into that before considering the PCM module. The PCM sees low refrigerant charge via the hi/lo pressure switch which is preventing the compressor from engaging.

[back2life]

bnaylor i gotta question,according to your test above, if the fan comes on when the ect is disconnected what does that prove? my problem is actually on a 95 grand am 3100 but it has this problem.

[richtazz]

As a safety measure, the PCM is programmed to turn the fans on if it isn't receiving a signal from the ECT. IF the car passes this test, it eliminates the fans, relays and fuses as the cause of the fans not operating.

[back2life]

foud out to be a bad connection at the fan plug-in. thanks for the help!