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Help on 996 AC Blowing Only Hot Air

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I have a 2003 996 Carrera in which the AC abruptly started blowing only hot air, regardless of settings.  Not a Freon charge or compressor problem.  I have been told that it is likely that the linkage from the motor to the "blending flap" that controls the mixture of heated to chilled air has broken or slipped off and is allowing only heated air into the mixing area prior to delivery into the cabin.


Here is my problem:  Although I have a PET parts diagram, all that it shows for the heating/AC unit is basically a "black box" without any details about what is inside.  Therefore, I cannot imagine what the arrangement of the temperature mixing flap and motor linkage to it might be or how I might make a repair, if that is possible.  I cannot see up into the unit to know what is going on.


So, here is my request:  Can someone with a Bentley manual take a look at the section on heating and air conditioning and let me know if there is anything resembling a picture or diagrams of what is inside of the unit so that I could imagine what would be required to repair the damage that my unit has experienced?  The factory repair manual is just as useless as the PET diagrams for this purpose and I hesitate to lay down $150 for the Bentley manual if it cannot address this problem.  


I would be very grateful for any help.  TIA.

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Thanks for the suggestion, but that fix is for the 924/944/968 group where you can actually see the parts.  Unfortunately, the 986/996 heating/AC unit is essentially a "black box".  I need to know what is inside it and how to make a repair, if that is possible.

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fpb111, thanks for the link. This looks like what I need to get started.  It would be great if the link in that document to "Porsche 986Air Box (3.31 MB)" was active.  Anyone have any idea of how I could get access to that document that is referenced?



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Trying to help out.  This is a parts diagram showing the various parts of the heater box, including the actuators: http://www.autoatlanta.com/porsche-parts/hardparts.php?dir=996-99-05&section=813-05


From what you described, it does sound like one of the valve actuators that controls the internal flap is not functioning.  Here is the best picture I can find of the 996 heater box...sorry, can't figure out how to put a picture in! Darn it.  Anyway, it does not show the internal flapper anyway.

Edited by DBJoe996
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  • 2 weeks later...

I had the same problem with my 03 996.  I ended up buying the black box on ebay from a junkyard that specializes in Porsche parts.  I was able to get the part that I needed and I was able to see how the box functioned to fix my blend door.  The piece I needed was small and I could not find it for sale from Porsche.

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  • 2 weeks later...
OK, an update.  I fixed the problem and I want to thank all those who contributed their helpful comments above.  The problem was that the linkage from the motor to the "blending flap" that controls the mixture of heated to chilled air slipped down off of the blender flap and allowed only heated air into the mixing area prior to delivery into the cabin.  The exact problem was that the two tiny plastic tabs that hold the final connection "plug" up from the controller motor linkage to the bottom of the flap broke off and allowed the "plug" to fall down and disconnect from the control linkage.  This can be addressed from the bottom of the dash by removing only the under dash cover and not the entire dashboard, etc.  


As av8sky has pointed out, Porsche, in its wisdom, does not provide that fragile part as something that can be purchased by itself.


After giving a lot of thought to this, I just bought a simple ca. 5" spring at a hardware store and, using a couple of "snag points" I found, stretched it over the top of the final "plug" to keep it up and connected to the blender flap.  Works fine now.

Again, many thanks to all of you who sent me your thoughts and information.


PS:  I cannot help believe that this is not, or will not be, a common problem for all of our Porsches that use this same Valeo HVAC system.

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