No AC
 

The AC was never very cold on the A8 since I bought it and I've always put it down to the lack of gas.
I dropped the car off to Audi for a AC Service.
Picked it up and it was cold, drove home and was the same.
The weather was it as hit as it has been so I waited till it was really hot.
Spent the day in Bristol and basically the AC the ****e. Pumping out warm air and not cooling at all.

Got home and phoned Audi.
They basically said it tested fine but it's in for a AC service not fault finding, so they just gas it up, do the other bits and ship it off.
If it's not working I can drop it in for a diagnostic session at £50.
Sod that, I went off to talk to a AC chap I know.I have no idea why I never seen him first.
He suggested I replace the pressure switch first.
So I did, no difference.

When I put vcds on the A4 I could see what's going on with the AC system but for some reason vcds does not have a label for HVAC system for the 8.

Does anyone know what each message block does in vcds or another way to test the AC system?

I has gas, I'm thinking it's the pump that's gone now.

Could also be the electric fan, if it doesn't kick in then neither will the ac.

Why do you think you have gas in the system?
does the system hold deep vacuum for long periods of time?

You may have a small leak so that systems passes vacuum test when being serviced, but it may lose gas, say, during a week of use.

Test the system with a good leak detector (a device that senses tiny amounts of gas) and make sure there are no leaks. You may need to recharge your system again to do that (if system will work again your compressor is OK). If leaks are found replace pipework/joints/condenser/evaporator. Replace drier barrel too. Make sure there are no leaks. Make sure system hold deep vacuum. Leave it overnight anded vacuum and see if how it holds vacuum. This will indicate there is no moisture and no leaks in the system.

Picked up on monday, no change.
De-pressed one of the schroeder valves and there was still gas in the system.
Did the same thing saturday when I fitted the pressure switch and still gas.

A output test via VCDS should start the fan up?
I'll do that later.

I had the same on mine. Ended uphaving it charged twice...would hold the cold for a day and then blow out hot air again.

There was a leak coming from the condensor due to a stone chip. I ended up having it replaced and it works a treat again.

Oli

we had a similar problem on my son's car, took it too an A/C specialist who put some sort of UV Dye in the system to detect the leak.

I might have some free time this week to get out to the car with VCDS and test/scan the system again and I don't get any further I'll drop it off to the local AC guys.

I can't do the leak test cause I don't have a sniffer, the glasses or the light, so its all VCDS.

Things to test:
AC fan.

That's all I can think of.
With no label file for VCDS its hard to check the meas blocks.

Pretty sure I had some labels showing when I had issues in my PF D3, at least checking for the pressure in the system. Or maybe I found a page elsewhere that told me which blocks to check.. It was more than 10 minutes ago, so memory a bit fuzzy :)

I'll have another search but found nothing so far.

I'm sure older VCDS had HVAC labels, but I also noticed that the recent versions don't.