I've had the refrigerant checked out by a transport (lorry) refrigeration engineer - all is fine. The compressor is kicking in and the air con is cooling somewhat. The passenger side is cooler than the driver side. If the fan is turned down it cools slightly more. I have checked both the filter and the cabin pollen filter. Neither affects the air con.

My guess is that it is related to the air flow over the evap, but haven't a clue where to start looking.

Any suggestions would be much appreciated.

Peter