Cooling fans not funtioning

[smits03]

Hi everyone,

I have a 1997 pontiac grand prix with a 3.8 engine. I have noticed that the cooling fans do not turn on. I have checked fuses, relays, replaced the temp sensor by the thermostat. I have also put 12v power to the fans and they both run. I don't know where to go from here, I do know that only one of the four wires going to the fans checks out to a ground, not sure if the other three are all power wires ro if i have a bad ground there.

Thanks

[Fivefingerdeathpunch]

You sure the motor is even getting hot enough to run them.

The fan speeds are 214º ans 226º IIRC.

Turn your AC on and see if one of the fans turns on.

[smits03]

I had it up to 250 according to the temp gauge last night and still nothing. I also noticed that when I turn the a/c the cooling fans do not turn on either.

[Rico]

Check relays?

[smits03]

Relays are good as well as fuses.

[Rico]

I'm trying to get the schematic, hold on.

[Rico]

Here is the chassis schematic

[Rico]

The first thing I would do is trip the relays with the low voltage control and see if fans come on. That will tell if everything is good from relay to fan. If fans do come on, then you probably don't have a control signal to the relay from the PCM. The schematics will make it a little easier; gives you wire color.

Control wires from the PCM out to relays are dark green for fan 1 (right) and dark blue for fan 2 (left). Take note of the chassis shcematic as there are three relays.

[smits03]

So i went to the parts store tonight to use their code reader. Come to find out that when the gauge on the car reads almost 250 the computer only reads about 225 and both fans turn on at that point. Is there any way to recalibrate the temp gauge or would it be easier to put in an after market temp gauge to be more accurate?

[Rico]

This doesn't make any sense. You said fans do not come on when AC is on. Either the PCM is bad or the AC pressure switch is bad.

Yes, you can change fan settings on the PCM. It requires a re-flash. Could it just be a bad temperature sensor?

[smits03]

I don't understand it either. I know that I need to recharge my a/c because it has a leak in it somewhere. Maybe there isn't enough pressure with a/c on to turn the fans on. Not sure just throwing that out there. Is it possible to recallibrate the temp gauge in the dash so it is more accurate?

[Scottydoggs]

if your a/c is not working, as in the clutch is not spinning on the compressor, the fans will not be coming on.

[Rico]

if your a/c is not working, as in the clutch is not spinning on the compressor, the fans will not be coming on.

Good point. I was assuming that the clutch was coming on.

[smits03]

So I recharged my A/C tonight and as I was charging it the fans turned on as the should as soon as the a/c compressor clutch started up. So all is well. Thanks for the help!!!

[Rico]

Good to hear.

[BillBoost37]

When the climate control sends the request for AC. it's only a request. If the pcm knows it's not turning the AC compressor on then the fans are also not commanded to come on.