memfisa@hotmail.co

Ok so my grandmother has a 2003 Pontiac Sunfire with the 2.2L DOHC engine, and recently her Rad Fan was going bad, her car kept on overheating and she would have to turn it off. So to diagnose the problem, first thing I did was turn on the A/C and the fan would not come on. So i checked her underhood fuses, and the 30amp MAXI fuse was blown for the rad fan. So i replaced her fuse, and her Rad Fan Relay.

This caused the Fan to come on but only when the A/C is turned on. After a few minutes of use the Fuse would blow again, and my next course of action was to change her Rad Fan motor, this solved the fuse blowing problem and now she can run her A/C and the fan will run no problem. But the problem she is having now, is the Fan will not automatically turn on when the car reaches the proper temperature when it should come on, the only time it will come on is when the A/C is turned on.

I've located a temperature sensor on the rear of the engine on what looks like the heater core valve, and I pulled the sensor wire off turned the key to the ON position, and jumped the wires but the fan still did not come on, all this did was cause the gauge to read very high.

What I am wondering i guess is, is there another temperature sensor which seperately controls the fan on another part of the motor? I have a new temperature sensor on hand, which i have not yet installed, but i don't see how this could be the problem because the in dash gauge increases in temperature as the engine warms up. It go all the up to 3/4 mark or further and still no fan activation.

Anybody have any ideas what this problem may be? I am beginning to think Body Control Computer, but i don't see how this could be either because her factory keyless entry FOB works fine. Also her automatic drivers side window will go down all the way.

There is a CEL/SES light on, and have yet to pull the codes but she informed me that her dealership told her it was leaking gas cap, which has been replaced and codes cleared and the light is back.

Any help is welcome!
Matt.

Smythers00

Hello up there in Retirement Living Heaven

Here's my two cents...

Short Answer

Try jumping that Engine Coolant Temp Sensor (ECT) again, but with the motor running.

Long Info About Your Cooling Fan Wiring

As you know, in terms of the heating and cooling system, the cooling fan is controlled through the PCM (Powertrain Control Module) receives info the A/C Pressure Sensor, the Engine Coolant Temp Sensor (ECT) and the Instrument Cluster (Microprocessor).

1. A/C Pressure Sensor - 3 wires (Red/Black stripe, Grey, Black) running to the PCM. This seems to be working fine, because when you turn on the A/C you get the cooling fan. The wiring diagram shows that turning on the A/C switch connects the ground to the Light Green wire which runs to the microprocessor, which in turn sends the signal to the PCM via a Tan wire. The PCM then sends power to the cooling fan relay via 1 Dark Green wire (which is grounded through the fuse which is hot at all times) turning the fan on through that single Light Blue wire.

2. Engine Coolant Temp Sensor (ECT) - 2 wires (Yellow, Black) running to the PCM. I think this is the sensor you were talking about, just to confirm - This is located on the coolant pipe at the right front corner of the cylinder head right behind the alternator. The engine might have to be running for this to work, I can't tell from the diagram.

3. The Instrument Cluster (Microprocessor) - Tan data wire from processor to PCM. Sends signals from all the temp control settings from the passenger compartment.

4. The A/C Compressor Relay Control - Dark Green/White stripe. Consists of the A/C Comp Clutch Relay which is connected to the A/C Comp Clutch (Dark Green wire) and the A/C Clutch Diode (Dark Green wire) This doesn't have much to do with the cooling fan. The PCM gets this info from the Microprocessor telling it to turn on/off the a/c compressor.

Hope that helps out.