My air con on my xtrail stopped working but appeared to be full. My local garage fitted a new air condensing unit(£450) but the air con still did not work. They have now bypassed the air con switch so my air con works when I turn on my heater,however now I cannot use the heater on its own. I feel this is a missdiagnose problem and the unit may have been fitted wrongly. Any advice would be most welcome.

Thanks