The incoming air is much to hot even with control turned down to 16C (or even 'LO').  Changed cabin filter and had the system re-gassed, which normally solves this problem.  However, it seems to have made virtually no difference to the incoming air temperature.

 

Could this be a faulty temperature thermostat somewhere in the system - or perhaps the dash control knob?

 

Driving today, for 30 minutes, with an indicated exterior temperature of 30C, I had the cabin temperature control down at 16C and the incoming air temperature felt at least as hot as the exterior temperature!  Surprisingly, when in desperation I turned the control up to 26C, the incoming air became distinctly cooler for about one minute!  Sadly it didn't last.

 

It's a 10 year old car and nothing lasts forever but I'd still be grateful for any pointers as to where I should be looking.

By the sounds of it, there could be a problem with the flap that controls the flow of hot air, but it could also just be the air con not working.

 

Does the compressor clutch kick in and the cooling fans run with the air con turned on?

Edited 7 August, 20169 yr by SuperbTWM

Climatronic?  Is it a Mk1 or Mk2?

Profile says 2 litre diesel so I'd guess it's a mk2.

It could be a stuck mixer flap, in which case you might get lucky with "flaperobics" (press ventilation system buttons semi-randomly for 5 minutes).

 

Or possibly an issue with the "sunlight sensor" (middle of facia top vent if you've a mk1) but that needs VCDS to test and confirm.

I'm having the same problem get someone with vcds to run diagnostic mine came up with the ac pressure switch it's located on the bulkhead between the brake servo and turbo behind a heat shield haven't got round to getting one yet to change mine but I've been told it has a valve to stop you loosing any gas oh btw this is on my mk1 petrol don't know if it's different on your diesel hope this helps

Yes it is Climatronic air con and also a MK2.

 

I also tried "flaperobics"  -  without success.  Both the cooling fans work with the air con switched on.

 

Thanks for all your responses but I guess I'm going to have to take it in for a diagnostic check up.