Radiator Fans not working

You too my friend.

Hi, my cooling fans are not kicking in. I checked the relays and appear to be good, but switched them out for others to double check and all is good. The temp rises at an idle and the templ light and check engine soon light come on, but when driving it drops down to a normal temp and the warning lights go off. I have heat so I'm assuming the thermostat is working. I jumped the connection where the engine diagnostic tool plugs in and the fans turned on right away. I've boiled it down to either the temp sensor or possibly the fuse before the relay, but I can't find the fuse. Any help is appreciated. Jeremy

Check ignition fuse 10amp and 15amp-also the coolant temperature sensor if all okay test the engine control module

The ign. fuses are good, but how do you test the temp sensor, I have a multimeter but don't know how to test this. I heard that it is powered with ohms, if that makes sense,

A bad coolant temperature sensor can be diagnosed by measuring its resistance and watching for a change as the engine warms up. No change, or an open or closed reading would indicate a bad sensor

The cooling fans are not kicking on when the engine heats up and I'm wondering if its a relay problem.. iv'e checked all the fuses and they are good ..and I don't know what else it could be ..would appreciate any help..thank you

The most likely suspect is a defective fan motor, but electrical tests need to be done to verify the rest of the circuitry is okay. To eliminate the relay, just swap it with a different one like it.

OK that helps I will replace the relay and see if that's the problem , the reason why I thought its the relay is both fans won't kick on.. but both fans may be bad....thanks for your input

I just want to make sure that you understand that these fans aren't even programmed to come on until about 226 -228 degrees which is probably much hotter than you are expecting. See if the fans come on with the AC. If they do you likely don't have a problem. I also believe this is a 2 speed setup so you could have lost just low speed too.

1995 Pontiac Grand Prix 3.1 liter, a/t, cooling fans won"t turn on.at all. I got the fans to run by jumper wire from relay locations. Both fans function, they just aren't being turned on by the engine temp sensor. I saw somewhere that the A/C system must be charged or they won't work, is that correct? Thanks for any help, Rick

The fans will come on when the correct coolant temp is reached no matter if the ac is charged or not.Unplug the coolant temp and see if the fan comes on?

have you replaced the relay???

1998 Pontiac Grand Prix mileage: 124,000. My car has the heavy duty cooling system (two fans). The air conditioner hasn't worked in a long time and I recently discovered that the cooling fans are not working either. I don't know how long ago they stopped working. When I put the car in diagnostic mode, both fans come on fine. Looking at my Haynes manual (severely lacking in electrical logic) it appears that the computer grounds the coil on the relays to activate the fans and air conditioning compressor. I opened up one relay and clipped a test wire on the computer side of the coil. As soon as I grounded it, the air conditioning compressor came on. I moved that relay into the other sockets for each fan and I could turn those on as well. As best I can tell, the computer isn't getting something it needs to turn them on. I don't feel the computer is messed up since it will turn them on when in diagnostic mode. There are no codes on the computer. The temperature gauge works fine. I just flushed the coolant and the low coolant sensor appears to work as well. What should I look for next and what would be the test procedure? This is not my daily driver but will be once the Firebird hibernates for the winter.

It sounds like you have a bad temperature switch or a bad temperature gauge. It is located on the lower right rear of the engine. Don't confuse it with the temperature sensor for the computer which is located on the top rear right of the engine.

I just has this problem, like you, my a/c compressor stopped . Without the a/c compressor to turn on the fans, the computer relies only on the temp sensor. The computer is set not to turn the fans on until about 230 or 240 degree's, that will be almost the red line on the temp gauge. As crazy as this seems, it is right. The temp will go up to almost the red line, then the fans come on , then the temp goes back down, then it repeats, crazy. If you fix the a/c the fans fill work like they used too, keeping your engine evenly cool. Trust me, fix the a/c.

My Grand Prix was just in to have my auto start re-programmed (AstroStart). I noticed that after it was programmed that my engine cooling fans don't turn off. Now, my car did this about 2,000 miles ago but the Service Engine Soon light came on and it was a bad thermostat which was replaced. Currently, the car sits at the right engine temperature and runs perfect, except the 2 engine cooling fans located directly behind the radiator don't turn off but rather stay turning all the time. It's about 20 degrees where I currently live and I know that when I warm up the car the cooling fans should not be running for obveous reasons. I don't know if the programming of my AstroStart has anything to do with it or maybe the timing was coincidence. I know this is abnormal because my car has not done this before. Do you know what the problem could be?

Hello –

To better assist you please let me know if your model is a GT, GTP or SE. Also I need to know the 4th and 8th digit of your VIN and your engine size in liter.

Please go to Auto Zone (AZ) or O’Reilly’s (OR) 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 and alternator.

It's a GT, 3.8L V6. The 4th digit of my VIN is W and the 8th digit is K.

I am not near an Auto Zone or O'Reilly unfortunately. And maybe I misunderstood you but the service engine soon light is not on at this time. I was curious if the codes you were referring too were the codes of the service engine soon diagnosis. So right now just the fans are running constantly with no service engine soon light on. Perhaps this will help you?

Hello –

Thanks for the info……..

The light does not have to be on to have thrown a code. Some – the light comes on – a code is thrown and when the key is cycled the light is off but the code remains.

Below is some info for you……….the last item is the actual fans are always on troubleshooting.

Inside Electrical Center At Right Side Of Engine Compartment

3.1L & 3.8L "W" BODY (GRAND PRIX)
NOTE: Cooling fan circuit utilizes 3 cooling fan relays. Relays directly controlling fan motors are 4-pin type and are referred to as No. 1 and 2. Relay determining cooling fan motor low speed or high speed operation is referred to as 5-pin relay in this test. See WIRING DIAGRAMS .


Cooling Fan Always On (3.8L)
1. If diagnostic system check has been performed, go to next step. If diagnostic system check has not been performed, see DIAGNOSTIC SYSTEM CHECK .
2. Turn ignition on, engine off. If one or both cooling fans are on, go to next step. If one or both cooling fans are not on, problem is intermittent.
3. If both cooling fans are running continuously, go to step 5 . If both cooling fans are not running continuously, go to next step.
4. Remove cool fan relay. If left cooling fan turned off, go to step 6 . If left cooling fan did not turn off, go to step 7 .
5. Repair short to voltage in right cooling fan supply voltage circuit. After repairs, go to step 8 .
6. Repair short to voltage in right cooling fan low reference circuit. After repairs, go to step 8 .
7. Repair short to voltage in left cooling fan supply voltage circuit. After repairs, go to next step.
8. Operate system to verify repair.

Hello - Hey - Also, it 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.

Hi,
Turns out I had the car brought in and it had a code of PO128 ECT below thermostat regulating temperature. The code was reset and my cooling fans operate as normal. Although they did not that my car only runs at 150 degrees down the highway, my car has always ran cool in the winter versus about just under 210 in the summer. I put a new thermostat in about a month ago and I know Grand Prix's like mine also run cool. I don't know why but I wonder if maybe that's why it takes my car so long to warm up, any thoughts? Anyways, it's fixed now and you know what the problem was.
Thanks,
ahenre

Hello –

Glad it is fixed.

Yes – the higher the thermostat the hotter the engine must get to open it. Some cars are pretty sensitive and will trip a light if the thermostat is a little slow…..though within operating limits.

Again, glad it is fixed…..thanks for letting us know.