Firstly I would check the A/C fuse under the bonnet.when sitting in the car with the engine running you should be able to hear the compressor clutch click loudly as you turn on the A/C than hear the cooling fan start up if no click try the wire going to the compressor, is it connected? the 4wd fuse will affect the A/C also you'll find the green light won't be lit too. try that finnally with the engine off try spinning the compressor by hand (the centre part of the pully) it should be free to spin. if the gas has escaped the A/C module won't allow the compressor to start. check the fuses first and the comp clutch wire. most common problems in my Jimny history
Good Luck.
Gav
