GelberPfeil

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.

DBJoe996

Okay...I know you posted this on RennTech and I've been trying to help. At least I know how to post a picture here...

DBJoe996

I also found this Pelican parts diagram. It is interesting because it shows the individual actuators and locations. How they work is another thing. I often find it helpful when poking around in limited space to stick my phone up in there and start taking pictures. Also, you say the unit is only blowing hot air. I am wondering if the AC is really kicking in. Have you tried lowering the AC temp to LO and see if the compressor on the engine is engaged? Might be a relay that is blown. For what it is worth, my flapper long ago blew most of the foam out the vents, but when I use the AC it works great. So just saying it might be the actuator motor for the mixing vent, or the AC relay/Fuse, but maybe not the internal flapper.
http://www.pelicanparts.com/catalog/...ELSWCH_pg2.htm

Paul Waterloo

The actuators are just a small electric motor with a rehostat associated with it. The purpose of the rheostat is to provide positioning information back to the HVAC head unit. At least on the old Audis of the same vitage, you can do an "adaptation" function (need tool to active that function), it runs the motors to each end of their stops and figures out what the resistance is and then stores it.

The head unit then tells the actuator to move, it has a "target" value, it then moves the motor which repositions the rehostat to the position it is commaded to. If the motor is fried or hung up, it won't work. Also, if the rheostat is broke, it can't report its position.

GelberPfeil

DBJoe996 and Paul Waterloo,

Thanks for your information and suggestions. I am going to check out some of the tests you have mentioned and see if my Durametric can provide additional clues.

My car has never blown any foam from the vents, but I am not sure if that is important in this case.

GelberPfeil

OK, an update. I fixed the problem and I want to thank all those who contributed 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. 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", 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, or will be, a common problem for all of our Porsches that use this same Valeo HVAC system.