Those Crazy Air Vent Configurations

[Sunroof]

Well, I bebuilt my A/C system last summer and found that the cooling is sufficent; however, no matter how I configure those three wonderful vent knobs (blue, red and black) I still get some warm air coming into the cockpit. Lets eliminate the windows, sunroof seals and rear pop-out windows. At high speeds it comes in near the footwells.

Lets see, Red knob, left, Black knob center, blue knob left..NO!
Reb knob center, black knob right and blue knob center..NO!

Like my ever fogging far left guage, I believe that the vent knob game to shut it all down to let the AC do its work is another inherent Porsche characteristic puzzle that once again makes the 911 as unique as they come..................as least on the older models.

Anyone suffer the same?

Regards
Bob
1973.5T

[david914]

I'm assuming that you know the three levers on the dash have absolutely nothing to do with the A/C system. If you have the top lever positioned as far left as it will go and outside air is still coming in, then you probably need to replace the gaskets on the butterfly valves inside the fresh air blower box. I'm not sure if they're still available from Porsche, but I've made my own from closed cell foam weatherstripping purchased at the home center. The most difficult thing is getting the airbox out, and it's not that bad. Just be sure to pay attention to how the valves and linkage is positioned as you take it apart. Also, clean and lube up the control cables while you're there. It'll work good as new when you're done!

[Sunroof]

Thanks Dave.
Yeah I know the AC is a very independent beast. The vents are at the knees at the knees (factory unit after sale dealer install), so you do not get that footwell cooling or the in-your-face breeze either. I am thinking the seals are fairly worn as well, but their is still too much air getting in for my comfort.

I am considering though placing a small hole with a deflector fitting into that cardboard blow tube that directs air to the knee vent. That way, their will be some cool air movement in the foot well and enough to put it at the comfort level.

Thanks
Bob

[FranksPlace2]

I have a 6 page article on the Porsche HVAC. It is a pdf, about 2 megs.

I'll send it to you if you PM me your email address.

Frank

[cmonref]

If you are getting warm air and it is coming thru the cabin heat system, and the heat lever (next to the hand brake handle) is fully down, then one or both of your heater control valves may not be completely closing. After they rust up, they bind in the slightly open position and some hot air from the heat exchangers gets thru and into the cabin. You may, or may not, be able to restore proper closing, or you might have to replace the heater control valve.