1999 Pontiac Grand Am



November, 18, 2008 AT 7:17 PM

Engine Cooling problem
1999 Pontiac Grand Am 6 cyl Front Wheel Drive Automatic 145000 miles

3.4L V6 I replace the water pump, the thermostat (twice), the cooling senor (twice) replace all fan relays, but the fans will not come on till it reach 220-225.

What else can I try? Is there another senor somewhere? I replace the one at the thermostat.


3 Answers



November, 18, 2008 AT 10:34 PM

Hello -

It looks like, based off of what you are saying, the fans are not coming on low....which is about 212 degrees. That is controlled by fan relay #1.

I am not sure how your gauge looks, but that is only a 8 degree difference. Is the car running hot?

When you start the car and turn on the AC, do both fans start up?

What I have done is give you information on the fan operation. The very detailed one names several relays, about 4 I think. So not sure if you have checked all of those.

Also, looks like you may have some recalls on your vehicle. The dealer may fix these for free. Please contact the dealer service department, give them the VIN number of your car and have them check on these to see if they apply to you.

Get back with us if this doesn't help.

Electric Cooling Fan System Notes

Dual electric cooling fans aid air flow through the radiator. The fans are driven by electric motors that attach to the fan shroud.

The fan motors are activated by the cooling fan relays.

Caution: An electric fan under the hood can start up even when the engine is not running and can injure you. Keep hands, clothing and tools away from any underhood electric fan.

If diagnosis is to be performed on a coolant fan electrical malfunction, refer to Powertrain Management.

Circuit Description
The electric cooling fan(s) are controlled by the Body Control Module (BCM) which enables the fans through the PCM. The PCM enables the ground path for the three cooling fan relays. The relay(s) are used to control the high current flow to power the cooling fan motors. When minimum cooling is required, the BCM will command the PCM to energize cooling fan relay #1 and since both fans are connected in series through the Mode Control relay, both fans will operate at low speed. When maximum cooling is required, the BCM will command the PCM to energize all three cooling fan relays. Power is supplied to the left fan through cooling fan relay #1 and is grounded through the Mode Control relay. The right fan is powered directly through cooling fan relay #2 causing both fans to operate at high speed.



November, 18, 2008 AT 11:29 PM

Reply to your questions

" It looks like, based off of what you are saying, the fans are not coming on low" The fans are always running on low when they do come on. The only way to get them to run on hi is to unplug the cooling senor. And I try another #1 fan too

" Is the car running hot?&Quot; yes and no. With a 15 lbs cap at times it will boil the water out.

" When you start the car and turn on the AC, do both fans start up?&Quot; Yes.

" The very detailed one names several relays, about 4 I think. &Quot; They are three relays a fan mode 5pin, #1 fan 4pin and #2 fan 4pin. All been replace

Is there another cooling/temp senor somewhere? I only know of one senor. It also works the temp gage too



November, 20, 2008 AT 9:05 AM

Hello -

Okay, first, is your Grand AM the SE or GT?? I know you have the 3.4L so I am going to assume it is the GT but want to make sure and what the 8th digit of your VIN and the 4th digit for body code.

The only switches/sensors I show is the coolant level sensor, the Engine - Coolant Temperature Sensor/Switch that you replaced, an engine temp sensor located on the dash, and the gauge.

I have attached the wiring diagram in two parts so you can read it. The first is the top of the second.

Next, you run Dex-cool in that. The problem they have found with that is it gums up. It is supposed to be flushed about every 30K. Your radiator may be clogged thus the overheating and boil over also causing your car to run hot, poor circulation. It may be throwing the sensors off especially if the coolant has broken down. I would definitely do a really good flush, me, I would replace the radiator if I had Dex-Cool in it all these miles, but that's me. The a good mix of the green, Prestone.

Are your heater hoses going in and coming out of the firewall both hot and do you have plenty of heat in the car with the heater on?

Let me know what you think about a good flush and do one other thing, please go to Auto Zone or O'Reilly's and for FREE they can pull the codes to the car. Most important: Once they check your codes, if they find something and you don't get it fixed and need to get back with us, please make sure you tell us exactly what the code was, number and all. Example, if the code was E0568 O2 Sensor bad. Then make sure you give us all of that. While there for FREE also they can bring their tester out and check your battery, alternator and starter.

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