Radiator fan won't stop

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Aznav
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Year and Model: 2004 XC90
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Radiator fan won't stop

Post by Aznav »

My radiator fan runs after the engine stops. Yes, I know it runs "purposely" at times when the car parks. HOWEVER, my fan will stop when the engine is off and then, maybe ten minutes later will come on by itself, only to run the battery dead. One person said a bad switch, and another said a bad module. Obviously, there is a giant difference in price. I am open to any suggestions. Thanks!

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ggleavitt
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Post by ggleavitt »

Should be a single wire connected to your fan, might be purple in color. That's the PWM from the ECU.

Start vehicle, turn on AC or anything that causes the cooling fan to run, then pull that single conductor and check if the fan stops. If it does, then you have validated control from the ECU to the fan. When vehicle is off but the fan in running, try that same test again. If nothing changes when you pull the single conductor, you have a bad fan assembly (controller). The controller is integrated into the fan assembly itself (there is no "switch" per se).

I would lean in the direction of a failed fan controller, the check above should help validate. There's DC voltage from the vehicle all the time on the assembly, and fan should only work when ECU directs. Did an S80 a couple years ago that had constant fan on after vehicle was turned off. Was a indeed a failed controller, the fan assembly was replaced with TYC brand.

Good luck with your repair.
2006 V8 AWD VOR-135k
2008 V8 AWD Sport-135k

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