lkstk

As the title suggests, my A/C is blowing hot. It’s a 2005 Allroad 2.7T manual (probably doesn’t matter).

I can’t tell if it’s blowing heated air, it’s 85° today. But when I adjust the temp up and down, I can hear the blend door operating. Everything looks good on the panel, all buttons react to input, but neither of my scanners will communicate with the A/C control unit. Which I believe is integrated into the panel. I know it’s not super accurate or reliable, but a basic gauge (doesn’t show psi) shows a charge on the low side. All three electric fans are operating. All fuses are good and I can hear the compressor clutch clicking on (with idle fluctuating) when I cycle the ECON button. And the ECON light doesn’t come on by itself.

Basic and unscientific logic makes me think that the panel/control unit is the problem, but I was hoping that someone else has BTDT with these same conditions. Any input is appreciated!

Johnbach

I just went through an AC repair on an older A6 C5, so I have a coupe of tips.

If you plan on keeping the car for some time (and with a manual Allroad you should) I highly recommend you to invest in a VAGCOM scanner. It provides better scanning and help than any other scanner you can get. Specifically for the AC part there is several optional debug tools. This is on the newer C5's like yours. Mine did not have that. There is a chance that the link is broken.

You can check to see if the compressor is running when the engine is running and AC engaged. Turn the AC all down, and look up from the from left corner. You may have to remove the splash shield if still there.

If the compressor doesn't run, you can check the power feeding the compressor. In the top left corner of the engine compartment, there is a connected assembled related to fans and coiling. The two connectors feeding fans are there. There is one single line connector that feeds the AC-compressor. Check if there is 12V when AC should be on.

Get a proper gauge to measure the pressure on the low side. It may be a simple issue of refilling the AC. You can get one along with a refill can from most auto shops.

lkstk

I had a Ross Tech dongle, but sadly I lost it in a move about a year ago. I’m using a middle range Autel tablet that works well for many cars, and can access all the control units on the C5, but gets less useful when you want to get actual values within a unit. The weird part is that the AC unit is the only thing that isn’t communicating at all. But the compressor is running, as well as the fans. Maybe I’ll break down and replace the VCDS, but I really hate spending money twice.

lounayong

A clogged cabin filter can restrict airflow through the air conditioning system, which can reduce its efficiency. Make sure the cabin filter is clean and replace it if necessary.

lkstk

After swapping out the control panel with another used unit, I can now communicate with the system. I pulled code 00818 on an OBD Eleven scanner which points to sensor G263 behind the glove box. Can anyone help with a part number for this item? It’s supposed to be behind the glove box. I can pull it for the part number, but if someone knows it, I would greatly appreciate it.