996 Wailing Sound

[dbookman]

Hi everyone,

I've got a somewhat perplexing sound coming that seems to emanate from somewhere deep in the dash upon start-up, and fades away within about 7-10 secs. It only happens occasionally, but when it does it can be quite loud. At first I thought it only did this when I started the car with the re-circ switch on, but I tried turning it off when the sound started and it didn't seem to clear it up. The sound eventually went away on its own.

I'm assuming its from an electrical motor, of some sort. Since I live in Florida, the A/C is generally in the ON position when I start it up. I'm going to try and remember to leave it in the off position upon start-up to see if that helps localize it.

Has anyone else had this problem? If so, I'd be interested in finding out how you fixed it!

Dave

[clord]

Dave....I think that I know what you mean. I also had what I would call a wailing sound on start up with the AC on. It occurred primarily on road trips in hot country where the AC would be left on. A Porsche dealer tech said it was the AC working fluid working through the expansion valve in the evaporator back to normal working pressures. Nothing to be done...just enjoy cool air. :D

[drsmeal]

There is a phenomenon called cavitation which occurs when fluid depressurizes so fast it allows bubbles of air to form in the depressurizing fluid. It is an EXTREMELY destructive process if it is allowed to occur for long. An example, a large dam once had cavitation in its bypass channels, the one that allow runoff from the dam, and the phenomenon chewed over 10 foot wide and deep ruts into the concrete and raw stone. I would be suspicious of this in any pressurized system that wails in pain, especially when the pressure differential would be greatest, i.e. when the AC is dumping high pressure fluid into a not-yet-pressurized part of the system. Maybe this has nothing to do with your problem but, personally, I'd get it fixed if under warranty.