Hi, I need help on this issue, I have a Mitubishi montero limited 2003.
When I turn the A/C off, it turns ON, and when I switch ON it turns the compressor off..

Does anybody knows what to check first??

Thanks Robert.

 

Well for starters, make sure it's not backwards day. After that, check the ac pressure switch, ac relay, and the ac control panel itself. Make sure nothing is shorted and causing that issue. The compressor needs 12 volts to activate the magnetic clutch so something is giving it 12 volts when it's not supposed to.