Questions and Answers

Cooling Fans Q. Hello, Vince, I have a problem with my car. The cooling fans and the A/C do not work. High temperature doesn't turn the fans on and turning on the A/C doesn't turn the fans on. Using a GM Scantool, I managed to turn on fan #2 and engage the A/C compressor. But, fan #1 will not turn on. From there, I checked to see if fan #1 relay was receiving power and ground - it does.

I then disconnected fan #1 and turned it on with the scantool and checked to see if the wire was receiving power and a ground - it tested good. Does this mean that fan #1's motor needs to be replaced? Also, where do I go from here to figure out why fan #2 (as well as #1) and the A/C do not turn on? I am quite certain that the A/C worked as little as three or four days ago. The fans haven't worked all summer.

Information: 1995 Pontiac Grand Prix SE, 3100 SFI V6 (VIN M), 70,000 miles, reman alternator installed 6-weeks ago, PS, ABS, FWD, A/C, flushed cooling system: 5/01/01, and Auto 4-speed trans. I sure hope you can shine some light on this situation.

Thanks a lot.

A. Here is how the system is supposed to work. The primary cooling fan operates when engine coolant temperature is above 226°F with A/C Off or 223°F with A/C On or Defrost functions requested and vehicle speed is less than 50 mph. When A/C refrigerant pressure is greater than 185 psi, then the cooling fans will run. When diagnostic trouble codes (DTC 14 ,15, or 70) are set then cooling fans will operate. The PCM will discontinue primary fan operation when the ignition is turned Off, engine coolant temperature falls below 210°F or A/C pressure drops below 189 psi with A/C selected.

Secondary fan operation begins when engine coolant temperature reaches 235°F with A/C Off or On. The secondary fan will operate if A/C pressure is above 136 psi with A/C requested and vehicle speed is below 50 mph . The secondary fan will discontinue operation if engine coolant temperature drops below 228°F, refrigerant pressure drops to less than 185 psi or the ignition switch is turned to the Off position.

It does sound like the primary cooling fan motor is bad. With the relay activated, see if you have battery voltage at the light blue wire going to the primary fan. Also check the black wire from the primary fan and make sure it is a good ground.

What you can do is run a jumper from the ground side of the motor to ground and a jumper from the battery positive to the light blue wire of the motor. If the motor doesn't run, you have a bad motor.

You can do the same for the secondary cooling fan to confirm that it is working as well. It is possible you have not met the conditions that will turn it on.

Additional Information provided courtesy of ALLDATA