Porsche Enthusiasts Club Forum

Irrespective of the temperature position setting I have warm air coming through the vents into the car.
I've changed the flappy valve at the rear of the engine bay (behind the MAF) so I assume its the sensor in the dashboard that's the problem. I understand it is located behind the small round pressing with the little slots?

Any advice on how to remove etc would be greatly appreciated.

Yes that is the sensor "behind" the circle with the slots (one neat trick with it is to create a bit of smoke in front of it and see if it gets sucked in, but this doesn't tell you whether or not the temperature sensing bit is working properly) - however from what I've read elsewhere I believe the next step is to check that the mechanism controlling the mixing of the hot and cold air is working, since when the temp slider is fully to the left I believe this should force the system to only give ambient air. This is also easier to get to as it's behind the centre console and can be accessed by removing the side panels; to get to the dash sensor I think you either have to remove the glovebox or the centre console to get behind the dash. Don't forget that there's also an external temperature sensor that's part of the system.

I'm sure I've seen this come up relatively recently on the 928UK list - you might try asking there, as there are people who understand the intricacies of the HVAC system far better than I do.

Hi

I had this exact problem a couple of years ago.....

Cure was....

First I changed the EXTERNAL sensor....which is in the air piping that goes from the back of the alternator to the inner wing...

Didn't cure it...

So next was the dash sensor...(behind the slotted disc on dash)....

Tried the blowing smoke at it trick with no result....

So changed it for a new one....and its an absolute pig of a job to do....you have to take most of the central console out to do it..and expect some skinned knuckles...

It was around £70 from memory from Porsche, and its a sensor with a very small fan attached...

But most importantly it worked.....but I emphasise it COULD be either the INTERNAL or the EXTERNAL....

All the best Brett

Thanks Brett

It's one of the winter project jobs

Hi Paul,

Sorry to be late contributing - just come across this thread.

The external sensor is easier to reach than the internal, so probably tackle this first in case it's the culprit. Can confirm that the sensor lives at the wheel well end of the alternator cooling hose. The hose attaches behind the front splash shield, but to remove this you have to remove the whole wheel liner.

You have to remove the centre console to get at the internal sensor. It's not difficult as I managed to do it! There are quite a few bolts/screws though including those holding on parcel shelves, and one that's accessed from glovebox. It helps to label and bag these as they are removed. I seem to remember that when you finally remove the centre console (you have to disconnect a number of electrical connectors for window switches, clock etc but I think they're all different so straightforward to reconnect, even so I found it useful to label connectors where there was a risk I'd forget where they went as you can see in the photo) the little sensor/fan is the only thing left attached to the console!

The Pirtle site has a very good write-up on removing the console. It's for an S4 but will be very similar. Look for the 'Interior - Centre Console' link under 'service procedures':

http://members.rennlist.com/pirtle/svc.html

With the console off the car looks as if a bomb has gone off inside, as per the pic of my interior below! But in true 928 fashion everything slots back together nicely. From memory the trickiest part of console removal was removing the plate around the transmission lever. There's a procedure for this in the workshop manual as it requires a particular sequence of moving the lever and flicking the detent locks underneath the selector plate. Like many 928 procedures it sounds more complex written down than it is to actually perform.

In the pic the console is lying on passenger seat, and you can see the internal sensor/fan at top left. My sensor is fine so I don't know a test procedure for it but I'm sure the Nichols site or Rennlist search will unearth one.

Hi

Just to add, you do not have to remove the whole centre console...the bit where the auto lever is can stay...you have to remove the upper parts though....

All the best Brett

Hi Brett,

It may be different on S4 v S2 but I thought I remembered my console all coming out as one piece? If not happy to stand corrected!

Cheers,

Adrian