Simple Air Conditioner Vent Question

[MWS]

I have an '09 C4S and when I have the AC on fully automatic mode it blows cold air from the expected vents on the dash as well as from the defroster vents regardless of the cabin temperature. I think it should not blow cool air from the defroster vents except when I select "Defrost." Is this normal?

Thanks.

MWS

[PAULSPEED]

Normal.

Paul

[wwest]

I have an '09 C4S and when I have the AC on fully automatic mode it blows cold air from the expected vents on the dash as well as from the defroster vents regardless of the cabin temperature. I think it should not blow cool air from the defroster vents except when I select "Defrost." Is this normal?

Thanks.

MWS

"...Is this normal.."

According to Porsche, yes. According to VW (and the ROW) no, NO..!!

Maybe now that VW "owns" Porsche this will finally get fixed in the same way that VW fixed their version of the Cayenne, firmware revision.

In the meantime the best procedure to use is turn the defrost/defog/vents "on" then back off. On my '01 C4 this procedure works.

This design flaw can prove to be dangerous, especially in your part of the country.

In July of '01 I was approaching Birmingham Alabama in the early evening just after dusk after a HOT day. Sporadic rain showers late in the afternoon early evening along the way. I was finding it a little hard to see the road ahead, bi-xenon projectors on, and finally came to the realization that condensation on the OUTSIDE of the windshield was getting denser and denser as I drove along. WHAT..??

Quick swipe of the wipers cleared up the windshield.

I had noticed a climate control anomally, had to reajust the temperature setting from time to time, during our drive in Europe. Mentioned it to the factory rep (shrug..) when we turned it in. Picked it up at POE at noon that July day. It wasn't until I got back home that I took time to figure out what was wrong.

On my '01 it only begins to route airflow from the defrost/defog/demist ducts once the cabin temperature is cooled down to within a few degrees of the temperature setpoint. I suspect it is designed this way so as to not discomfort the driver and passenger with too much COLD airflow directly to the face an upper body. We might like to set directly in front of a window air condition to initially cool down coming inside on a HOT day but once our comfort level is reached we move away to enjoy the room's "general" coolness.

Oh, you can improve the functionality of your A/C system fairly dramatically by installing a shut-off valve in the hose to the heater core. Shut the flow off in the summertime and the A/C compressor duty cycle will fall dramatically as will fuel consumption, abet not so dramatically.

Edited October 4, 2009 by wwest