V50 AC and Speedometer Error

Those symptoms suggest a cooling system problem. The AC control unit itself might be bad, stopping the system from starting. Did you check the refrigerant level? A sensor fault is possible, but check the easy stuff first. Has any work been done on the engine cooling system recently?

Thanks. The refrigerant level is fine. No recent work on the cooling system either. Could a sensor calibration fix this, or is a bigger sensor problem more likely with these symptoms?

With the speedometer error and AC issue, calibration probably won't fix it. The error memory likely has a code for the sensor or control unit. Take it to a shop with Volvo diagnostics for a proper diagnosis before replacing parts.

Thanks for the advice. I took it to a Volvo specialist. It was a faulty AC control unit, like you thought, and the temperature sensor was bad too. Total cost was 980€. Thanks for pointing me in the right direction!