Radiator fans not working

2003 PONTIAC MONTANA
169,000 MILES • 3.4L • 6 CYL • AUTOMATIC
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LAURIE DAVIS
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The fans do not come on. I have installed new sensor and all relays the fans are not locked up. The fans will operate when using a jump wire. This caused the overheated engine to blow a head gasket I have replaced the gaskets recommended and reassembled the motor. Vehicle is running as it did prior to the blown gasket. I fear it will blow the gasket again. Diagnostics has been done and each time I replace the parts it indicates is the problem, retesting gives a new different result. I have done everything but still the fans do not come on. What else could be the problem? How do I fix it?
Apr 25, 2017 at 10:31 AM
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HMAC300
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I have seen the PCM go out and cause this issue I would get a rebuilt unit by searching Google or Ebay. Here is a wiring diagrams for the relays in case you need it.
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Apr 25, 2017 at 12:22 PM
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ART SMITH
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Two wheel drive automatic.

Fans not working fuse okay. How do I check further?
Jul 24, 2018 at 10:29 AM (Merged)
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SATURNTECH9
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https://www.2carpros.com/forum/automotive_pictures/416332_2000_pontiac_coolant_temp_sensor_1.jpg

I posted a diagram of where the coolant temperature sensor is unplug it and with the engine idling jump the two terminal's together on the connector harness with a jumper wire. If the fan kick's on replace the coolant temperature sensor.
Jul 24, 2018 at 10:29 AM (Merged)
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JOEYB69
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The radiator fan is not working. I have replaced the fuse.
Jul 24, 2018 at 10:29 AM (Merged)
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RASMATAZ
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Check and test the fan relay and the coolant temperature sensor.
Jul 24, 2018 at 10:29 AM (Merged)
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BAROSJOEY
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Six cylinder two wheel drive automatic.

Cooling fans do not kick on. Only when you turn on A/C. Already changed thermostat and sensor on housing also changed both fan relays.
Jul 24, 2018 at 10:29 AM (Merged)
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BLUELIGHTNIN6
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There are three relays and two maxi fuses that need to be checked. Here is a guide to help you test the relays and a wiring diagram so you can see how the system works:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

and to test the wiring:

https://www.2carpros.com/articles/how-to-check-wiring

Use the test light to check for power at the relay.

Check out the diagrams (below). Please let us know what happens.

Cheers
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Jul 24, 2018 at 10:29 AM (Merged)
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BAROSJOEY
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Thanks for your help on this. It turned out the fan control driver was out in the PCM. So I got a used one and plugged it in all fixed! I love this site.
Jul 24, 2018 at 10:29 AM (Merged)
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BLUELIGHTNIN6
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Good to hear, please use 2CarPros anytime we are here to help.

Cheers
Jul 24, 2018 at 10:29 AM (Merged)
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DCMANNIN
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My cooling fans will not engage. I have replaced the relays in the main fuse block, if I use a jumper wire in the fuse block where the relay is the fan runs. Not sure if there is another relay. Any Ideas? The two relays I replaced were aux engine cooling fan relay and radiator cooling fan relay.
Oct 1, 2019 at 5:01 PM (Merged)
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RASMATAZ
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I have seen this problem before it ends up being the PCM fan control driver has gone out making the fan run only when the AC is on. I would get a used one because new will require to be reprogrammed wich will cost about $130.00. Here is the PCM location below.

Check out the diagrams (below). Please let us know what happens.

Cheers
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Oct 1, 2019 at 5:01 PM (Merged)
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KRISTENLEE
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This post is spot on! Fixed my car with a used PCM I got for $120.00. All fixed. ;)
Oct 1, 2019 at 5:01 PM (Merged)
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BAYHORSE
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02 Pontiac Montana engine cooling fans wont engage with coolant temp. have had to 206 deg.wont engage if I disconnect temp. sensor fans engage. both fans have voltage but not getting ground. temp. guage works and when connected to computer scanner shows temp. also stays in closed loop from cold to hot.
Oct 1, 2019 at 5:01 PM (Merged)
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HMAC300
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check ground at lh rear of engine then check items in pic. it may be that the relays need dielectric grease and tweaking to get correct power to fans..other wiles have apro scan for code and check ground wire from fans to lh rear of engine. also check ground to center fan relay in pic. may not be making contact
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Oct 1, 2019 at 5:01 PM (Merged)