Vectra AC Compressor Failure

I've seen similar HVAC issues. Before blaming the control unit, check the refrigerant level and look for leaks. Low refrigerant can cause these symptoms. Also, confirm the compressor clutch is getting power when the AC is on.

I haven't checked the refrigerant level, but it was charged six months ago. Could a slow leak cause this? Could a faulty compressor clutch relay cause similar problems?

A slow leak could explain it, even after a recent recharge, and would prevent efficient cooling. A faulty relay is also possible and easier to check. But with the error code and symptoms, a bad AC control unit is still likely. Get a proper diagnostic at a workshop, including a refrigerant leak test.

Took it to a workshop. They diagnosed and replaced the AC compressor and related parts. Cost 980€.