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heater cut out when hot on 993


19 Feb 2004
Just got the car back from a service at Camtune - apparantly the heater cuts out when set to its hottest. They didn't have time to investigate. Any thoughts ?

Migration info. Legacy thread was 13586

I have a 1995 993 that does a similar thing. When the engine is hot the heater is either hot or cold with very little in between. As I have only had the car for a few months wasn't sure if this was one of those "special" features of 993 ownership! This weekend it became very apparent as I covered several hundred miles and was unable to keep a constant temperature in the car, not so much a problem for me but the mrs wasn't too happy!

Was going to investigate further on this board but you beat me to it, will be interested to hear peoples thoughts.



Migration info. Legacy thread was 13588
I remember reading something in 911Porsche magazine where they suggested that the linkage that opens flaps for hot or cold air can become broken. That could explain your problem.

Mine is more obscure - with the fan on high, and temperature on low, I get a blast of cold air. As I increase the temperature the air gets warmer, but the air flow gradually reduces.

Migration info. Legacy thread was 13610
Fixed ! It seems that the front heating fans will not work on hot, if the rear blower (in the engine compartment) is at all faulty - test with ignition on, engine not running, and temp and fan both at full - it is easy to hear if running. In my case replacing the fuse (again in the engine compartment) rectified the problem. Lots of information is buried in the Renlist forum, of which two useful threads:



Percy1 - not sure if this is also your problem. There does seem to be another common fault with the servos which open those flaps at the front. Another useful thread (or search for hvac):


Migration info. Legacy thread was 13705

Thanks for the tip, will have a fiddle this weekend (weather permitting) and see if its the same.

Migration info. Legacy thread was 13706

Have tried to remove the plastic cover that goes over the heater servos in front of the windscreen with out success. Does anyone know how this comes out, there doesn't appear to be any screws holding it in place but it seems fairly solid. The link above is for a 964 and my 993 seems different.

Think I have narrowed the problem to the passenger side servo as everything else seems to work OK, once I can get the cover off I will be able to tell for sure.



Migration info. Legacy thread was 13912

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