Cooling fans not turning on properly

Tiny
DOUG S.
  • MEMBER
  • 2002 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 140,000 MILES
It seems that my cooling fans are not coming on properly. They do work, I have replaced three relays and a fuse on the car. The temperature gauge will go up to the 3/4 mark, then the fans come on but only cool it down the the 1/2 mark. If I am driving on the highway, the temperature gauge stays between 1/4 and 1/2 mark. Also, I did replace the fans. Is this normal for this car? I have only had the car for three months?
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Friday, March 5th, 2010 AT 2:34 PM

21 Replies

Tiny
JDL
  • EXPERT
Hello,

I would try replacing the engine coolant temperature sensor which controls the fans via the PCM. Here is the fan wiring diagrams so you can see how the system works and the location of the sensor with a guide to show you the steps to replace it:

https://www.2carpros.com/articles/coolant-temperature-sensor-cts-replacement

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

Cheers
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Friday, March 5th, 2010 AT 2:48 PM
Tiny
LVZNLO
  • MEMBER
Thank you for this post I got the sensor for $28.00 it fixed the problem! I love this site.
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Wednesday, September 26th, 2018 AT 11:45 AM
Tiny
75MIKE
  • MEMBER
  • 2002 BUICK CENTURY
  • 150,000 MILES
All the fuses are good. There is no power at the plug that connects to the fans. I have checked all the fuses and they are good. The fans will not even turn on with the AC on. I can hook up a jumper wire to the fans and they will work.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check the fan relays and the computer controlled circuit of the relays and also the coolant temperature sensor.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
MANDINGOCREED
  • MEMBER
  • 2002 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 20,000 MILES
My radiator fans will not come on normally, but once I turn on the heater the radiator fans will come on it does not seem like it is a fuse. I did change every fuse that was related to the radiator fans but still nothing. What could this be?
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
BMRFIXIT
  • EXPERT
If overheating and fans no coming on:
Check intake manifold gasket for leaks
Check for codes
Check relays and coolant sensor
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
DEAN MIXON@YAHOO.COM
  • MEMBER
  • 2002 BUICK CENTURY
  • 17,500,000 MILES
Cooling fans will not come on.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
What have you checked so far? Fan motor? Fuse? Relay? Is the engine overheating?
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
JUICEBOX
  • MEMBER
  • 2003 BUICK CENTURY
Six cylinder front wheel drive automatic.

3.1 overheating, while idling and when the engines is up to temperature, the fan never comes on. With the AC on high both fans come on. Thermostat is not stuck as I have heat on both hoses. What is left for me to check? Relays? Should I try to switch them while the car is running and up to temperature? There is three for the cooling system, not sure which one controls what. Could it just be the radiator cap?
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
LEGITIMATE007
  • EXPERT
Yes, it could be the radiator cap. The cap should be 15. Lbs. Also the cooling fan relay is probably the culprit if not the radiator cap, do not switch while running, your liable to zap something. We know the fans are not at fault because they come on with A/C. So relay, and cap.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
JUICEBOX
  • MEMBER
Thanks, will look into both.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
LEGITIMATE007
  • EXPERT
Awesome, keep me posted.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
IMTWEAKINIT
  • MEMBER
  • 2000 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 69,000 MILES
Checked fans and they do work, checked all fuses and relays all seem good. AutoZone said it was my temperature switch but does it regulate my fans turning on and off or does it just tell the gauge in the car what the temperature is? I have the temperature switch but do not want to put it in until I can get this question answered. Please help
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
The switch sends a signal to the PCM which then goes to the relay and then the fan.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
GORDON321
  • MEMBER
  • 2003 BUICK CENTURY
Six cylinder front wheel drive automatic 100,000 miles.

I just replaced the thermostat, radiator cap, coolant sensor, and checked all relays on my car. The cooling fans still are not coming on when the car reaches normal temperature. Then it starts to go past the normal temperature and the fans will not come on but when I unplug the coolant sensor or turn the air conditioner on both fans come on. Is there another sensor, switch or anything else that controls the fans? If so what and where is it located? Please respond ASAP. By the way nothing is stopped up.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
BLUELIGHTNIN6
  • EXPERT
Three cooling fan relays and an engine coolant temperature sensor are easiest and cheapest on the circuit that could cause this issue. If they have been checked/replaced already than all that is left is the power-train control module (PCM).
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
BENJAMINP
  • MEMBER
  • 2001 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 63,000 MILES
The cooling fans will not come on ever. The car runs and then overheats because the fans never come on and also the A/C will not come on. Have checked all relays and fuses, they all work. Any advice is helpful.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
RASMATAZ
  • MEMBER
Check and test the coolant temperature sensor. If it has an engine temperature sending unit test that too.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
BENJAMINP
  • MEMBER
Thanks for the quick response. I forgot to mention this, I originally got the thermostat replaced and then these problems occurred (I do not want to deal with that mechanic any more though). Then I replaced the coolant temperature sensor. This is what I originally thought was the problem, yet still has overheating problem. I will check on the temperature sending unit.

Would the temperature sending unit also not permit the AC to not come on?

And thanks for the advice.
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Wednesday, September 26th, 2018 AT 11:46 AM (Merged)
Tiny
MANDINGOCREED
  • MEMBER
  • 2002 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 20,000 MILES
My radiator fans will not come on without turning on the heater there for my car runs hot. I have changed several fuses but still it will not come on. Normally what could this be?
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Wednesday, September 26th, 2018 AT 11:47 AM (Merged)

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