Air-con Error codes:

The air-con has a diagnostic mode to help identify issues, the most common error is 21 - Solar Sensor you can get this if there is no direct light on the sensor, even the tax disc casting a shadow will evoke the 21 error, shine a torch on the sensor (top left of dashboard on RHD models) to check if the sensor is working correctly during the diagnostic mode.

If you have low gas in the system you will get a whole load of errors, a re-gas will normally remove most error codes.

When the air-con is running if there is a metallic or rumbling noise from the compressor it is stuffed.