Engine overheats but the cooling fans do not turn on unless the AC comes on

Tiny
BRANDON STORCH
  • MEMBER
  • 2003 CHEVROLET MALIBU
  • 3.1L
  • V6
  • 2WD
  • AUTOMATIC
  • 195,000 MILES
The car itself overheats even after new water pump was installed, thermostat was installed, all relays and fuses were checked, system was bled out. Today I noticed the fans were not working. But would work if you turn the AC unit on. And if you turn the AC unit off the fan switch continue to work. Question is, why will the cooling fans not turn on when the temperature which is the point to need the cooling fans to be activated?
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Tuesday, August 7th, 2018 AT 8:23 AM

14 Replies

Tiny
PATENTED_REPAIR_PRO
  • EXPERT
You might just have a faulty relay. Check the fuses first of all as shown in this diagram. Then if okay, try a new relay to the affected right or left fan.
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Tuesday, August 7th, 2018 AT 9:18 AM
Tiny
BRANDON STORCH
  • MEMBER
All the fuses and relays are good to go, but still the fan will not come on and causing the engine to overheat unless the AC is turned on.
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Tuesday, August 7th, 2018 AT 9:31 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
How do you know the relays are okay?
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Tuesday, August 7th, 2018 AT 9:32 AM
Tiny
BRANDON STORCH
  • MEMBER
Brand new.
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Tuesday, August 7th, 2018 AT 9:33 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Okay, do you have a voltmeter or at least a 12 volt test light and a scan tool or code reader and if so are there any codes?
Also, which fan is it, left or right or both that does work when the AC is turned on?
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Tuesday, August 7th, 2018 AT 9:39 AM
Tiny
BRANDON STORCH
  • MEMBER
No codes, both fans fail to come on, but will work after the AC is turned on and will continue to work continuously after the AC has been turned off.
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Tuesday, August 7th, 2018 AT 9:46 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Have you done anything else such as replace the coolant temperature sensor?
So no P0480 or P0481?
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Tuesday, August 7th, 2018 AT 9:54 AM
Tiny
BRANDON STORCH
  • MEMBER
Have not done that yet. Was next step.
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Tuesday, August 7th, 2018 AT 9:57 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Do you have a scan tool that can turn fans off and on?
If you do this step will both fans run on low speed or not?
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Tuesday, August 7th, 2018 AT 10:01 AM
Tiny
BRANDON STORCH
  • MEMBER
No I do not.
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Tuesday, August 7th, 2018 AT 10:02 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Let me know if both fans run at low speed or not when doing this.
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Tuesday, August 7th, 2018 AT 10:07 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
I think there would be a code set if it were a problem with the wiring. If the fans run in that test, I think you should give a new coolant temperature sensor a try.
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Tuesday, August 7th, 2018 AT 10:13 AM
Tiny
BRANDON STORCH
  • MEMBER
I will pick one up on my way home see if it works. I will let you know.
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Tuesday, August 7th, 2018 AT 10:15 AM
Tiny
PATENTED_REPAIR_PRO
  • EXPERT
Okay.
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Tuesday, August 7th, 2018 AT 10:57 AM

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