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How to diagnose a 944 climate control issue

  • 1989
  • 944 S2
Mileage: 
135 000
Heating and Ventilation
Gig Harbor, 
Washington

My 944 recently suffered from "all heat all the time".  My troubleshooting process when like this:

#1 - The most frequent climate control issue with 944's is broken plastic clips that hold the push rods for the air damper doors.  Sure enough, I had a broken clip.  I replaced the clip and now I have "no heat all the time". 

#2 - The second easy thing to check is the vacuum acuated heater control valve.  But because I had full on heat we know that it is either operative or stuck open.  Just to be sure, I tie-wrapped it in the open position.  But, I still have no heat.  The no heat condition exists regardless of where you set any of the system controls.

Don't know if it helps any but before the system failed the heat was pretty tempermental.  When the thermostat was set at low temperatures, the system would oscillate between full heat until it got uncomfortable and then no heat until, again, it got uncomfortable.

I've not found a source of information about how to proceed with troubleshooting once the plastic clips and heater control valve are ruled out.  Any advice will be greatly appreciated.

Bill

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