maclaw81

Hey guys - so I've got a 991 C4 and there is an odd sound coming from my dash. It sounds like its coming from the vents opening and closing during the start-up and turn off procedure. It's already been in a couple of times with various fixes having been done, most recently the heater box being replaced. It seems to just happen when it's cold out and I've been running heat through the vents. It's never happened during a cold start in the morning. Anyone have any idea what this sound is? Is it the vents? I've attached a video.

Thanks!

Dyim

I have something similar during shut down. Doesn't happen all the time. Much shorter duration though. 2013 C2S.

Didn't do anything about it. Almost out of warranty now.

worf928

It sounds to me like an unconnected vacuum changeover valve. If this was an older Porsche I would bet that when the heater core was R&R'd that one of the VCVs was left disconnected or poorly connected. However, I would have hoped that by now that vacuum control of HVAC was a thing of the past. Maybe not.

kayjh

What year is the car?

CSK 911 C4S

That would be annoying.

I hope they figure it out...... there's a little servo or diaphragm that is not very happy in there somewhere.

maclaw81

Hey guys - thanks for the replies. It's a 2013.

Like I said in my initial post, it seems to only happen when it's cold out and I'm directing heat to the windshield - and even then, not every time. I've followed back up with the shop and they are researching it further. During the start up/shut down procedure, what is making that opening and closing sound? Could the problem be something as simple as needing lubrication?

plenum

LOL! You must not have been following the "Ongoing COV problems" thread!! No heat to the cabin is one of the primary complaints from .1 owners and usually it is a COV failure, which is part of the broader Vaccum system. Not sure in this particular case a COV would be controlling the flap to direct heat to windshield vs. the exchanger COV that directs heat to the cabin ducts generally.... But you never know, right?

plenum

You might also consider that only at start-up you have pre-settings for air circulation kicking into action. Maybe part of the memory function set to the key? I can't remember how that is set-up, but the car may be opening / closing a flap for circulation of fresh air vs. recirc, etc. Just a guess. And sure, since the flap is mechanical, it could be that something is out of wack and what you hear is binding or rubbing of two parts in conflict.....

worf928

That's the way it works in - at least some - older Porsches.

Venice991

Did you find a solution on this? I have a similar noise on my car, but it's much quieter, and occurs at stop lights, and at shutdown.