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

2003 CHEVROLET MALIBU
195,000 MILES • 3.1L • V6 • 2WD • AUTOMATIC
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BRANDON STORCH
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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?
Aug 7, 2018 at 8:23 AM
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PATENTED_REPAIR_PRO
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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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Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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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.
Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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How do you know the relays are okay?
Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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Brand new.
Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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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?
Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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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.
Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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Have you done anything else such as replace the coolant temperature sensor?
So no P0480 or P0481?
Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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Have not done that yet. Was next step.
Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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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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Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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No I do not.
Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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Let me know if both fans run at low speed or not when doing this.
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Oct 28, 2020 at 6:09 PM
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PATENTED_REPAIR_PRO
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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.
Oct 28, 2020 at 6:09 PM
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BRANDON STORCH
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I will pick one up on my way home see if it works. I will let you know.
Oct 28, 2020 at 6:10 PM
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PATENTED_REPAIR_PRO
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Okay.
Oct 28, 2020 at 6:10 PM