I'm trying to figure out whats going on with my a/c. I have an 03 trailblazer LT. My A/C wont blow cold yet it is full with refrigerant. When I am at idle and parked my will rpm start to go up and down.(usually when the compressor cycles on and off). It sometimes will drop to zero causing my car to shut off. This only seems to happen when I have the a/c on amd I'm parked or at a light. I recently cleaned my throttle body thinking that may solve the problem but still nothing. I dont k ow hiw relevant it may be but ive also change my blower motor resister because my a/c was nit working on the 1st and 5th setti gs but is working now but still no cold air.