Overheating and the coolant fans do not turn on

Tiny
ROGER PECH
  • MEMBER
  • 1999 PONTIAC GRAND AM
  • 2.4L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 207,000 MILES
I just got the car listed above. I'm having trouble with my cooling fans switching on. My coolant sensor tells me the temperatures of the coolant but won't switch fans when the gauge passes the middle and my car seems to overheat. I've unplugged the sensor with the ignition on and the fans turn on but once I plug it in they switch off. I don't know what to do anymore and I need help before I start spending money on replacements I don't need!
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Sunday, January 5th, 2020 AT 1:17 PM

2 Replies

Tiny
KASEKENNY1
  • EXPERT
Okay. We need to start with what the BCM is seeing as the coolant temp. The way this works is the BCM monitors the temp and when it gets high it tells the PCM to ground the relays and turn the fans on. This means we need to see if the BCM is seeing the proper temp. If it is then we need to look at the PCM to see if it is getting the command to turn them on. If it is getting the command then we can assume that the PCM is the issue.

However, I attached the testing for the fans. It is lengthy but it will lead us to the issue as well.

Let me know if you have questions or what you find. Thanks
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Monday, January 6th, 2020 AT 5:05 PM
Tiny
TOUGHDIVER
  • EXPERT
There are two coolant temperature sensors on the engine one on top and one on left side in the cylinder head for the cooling fan it has one wire and it grounds the relay when car overheats. You can ground it for a test be sure to check the fuses and relays first. I am attaching wiring diagrams fuse and relay location below for you to refer to. Let us know if this information was helpful and if you need more information.

Thank you
Joe T.

https://www.2carpros.com/articles/how-to-check-a-car-fuse
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Monday, January 6th, 2020 AT 5:30 PM

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