Mercedes A Klasse Diesel AC Problem

That sounds rough! I had a similar issue with my old Vauxhall Corsa. The AC stopped working completely, and like you, I checked all the basic stuff first. It ended up being a faulty pressure sensor that was stopping the compressor from kicking in. Have you checked that? Also, is the compressor clutch engaging when you turn on the AC? You should be able to hear a click.

Interesting! A faulty pressure sensor is not something I had considered. Where is the pressure sensor typically located? And how would I check the compressor clutch? I haven't got any fancy AC diagnostics tools, just basic stuff really. I am trying to keep costs down.

Okay, so on my Corsa, the pressure sensor was located near the condenser, at the front of the car. You might need to remove a plastic cover to see it. As for the compressor clutch, with the engine running and the AC switched on, have a look at the front of the compressor. The clutch is the part that engages and starts the compressor spinning. If it's not engaging, it could be a sign of low refrigerant, a faulty clutch, or a problem with the electrical supply to the clutch. Honestly, without the right tools, it's a bit tricky to diagnose properly. Maybe best to get a mechanic to take a look!

Thanks for the input, I really appreciate it. I think you're right, I'm fighting a losing battle without proper diagnostic tools. I took it to a local garage. Turns out it was a faulty valve as I suspected and a small refrigerant leak. Cost me 1050€ in the end, but at least it's sorted now and the AC is blowing ice cold again!