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front rads fans always on

modlin
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modlin Member

modlin

Posted
Posted

Hello...need some help with my 2009 Carrera 997.2

  • hvac blower stopped working - it was dead, replaced it...now all is ok with heat/ac
  • initially, was looking for a bad relay controlling blower on Relay Support No.1...and here, I probably screwed something up with pulling and switching relays while testing, that started to affect front rads' fans
  • now, both rad fans running non-stop@ hi speed...while driving or stopped/idling...they stop when car is being turned off
  • looks like my 'fat fingers' caused some kind of 'open' condition for signals to those fans
  • never heard these fans running before....if they ever did, probably on low speeds @ very hot days situations

All input will be appreciated.

 

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JFP in PA Member

JFP in PA

Posted
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Posted

Welcome to RennTech :welcomeani:

 

This is going to be both complicated and potentially expensive.  Your car is equipped with pulse width modulation controlled fans which use a signal from the DME to control their fully variable speed controllers.  If the PWM fans have gone bad, there is no fixing them, they have to be replaced, and they ain’t cheap.

 

I would suggest scanning the car with a Porsche specific scan tool (PIWIS or Durametric) and looking at two things:  Check your engine temperature sensor for correct readings, and test the fans them selves.

modlin Member

modlin

Posted
  • Author
Posted

Thanks for the reply JFP.

Additional info: with car running and hvac system on, when I pull out fuse @B10 pos., hvac system goes off, fans are still full blast...but when I put fuse in...havc system comes back on with fans slowing down to a stop and then after few seconds coming back @ full speed again

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JFP in PA Member

JFP in PA

Posted
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Posted
2 hours ago, modlin said:

Thanks for the reply JFP.

Additional info: with car running and hvac system on, when I pull out fuse @B10 pos., hvac system goes off, fans are still full blast...but when I put fuse in...havc system comes back on with fans slowing down to a stop and then after few seconds coming back @ full speed again

 

It sounds like the fans are getting an erroneous signal.  You need to scan the vehicle, pulling fuses is not going to isolate the issue.

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