MY 94 dodge caravan's air conditioner is not working. Tried to recharge but it would not take gas on low pressure side and would not release gas on high pressure side while the system was running. The compressor cycles for 2-3 seconds and shuts down. Only warm air blowing out now. Service station charged system, supposedly, but only warm air coming out. Need help from the gurus of the A/C gods. Thanks, Jonathan.