hi i tried to use my air con toady but only warm air came out so i went through all the heat settings and the only change seemed to be when i put it on hi setting then it got hot but no change on anyother settings just warm. anyway i stoped the car and tried aircon again and with no music or reving when it powered up there was a hissing noise, the only thing that used to happen when i started it was a slight rumble in the car when it powered up but now i have hissing. is it fooked? what should i do, and who should i see, can i check anything myself. cheers in advance peeps.