a/c system cools at idle but shuts down when press accelerator

Asked by Jul 31, 2013 at 10:20 AM about the 1998 Chevrolet Express G1500 LS Passenger Van

Question type: Maintenance & Repair

system is cool at idle.i have changed everything from compressor to dryer to expansion
valve.high pressure line wont warm up.. high pressure read 100 and low pressure 35 at
idle. please help. i dont know what else to change or repair. the whole system has almost
been replaced.

3 Answers


Does the system get hot or just shut off when you press the accelerator ? If it just shuts "down/off" during acceleration, it could be the ECU is telling the A/C pump (out under the hood) to shut off while you accelerate and then it allows the A/C pump to come back on once The ECU is designed to tell the car what to do under every scenario such as when you pass or ask for "quick" throttle with the car hot and A/C on - the ECU sense the throttle plate opening and the driveshaft speed at that time, then will tell the EGR to close, the A/C to shut "off or down", the injectors to dump in more fuel and the transmission to shift down within milli-seconds and will keep that scenario running until you lift your foot off the pedal (thereby closing the throttle body valve opening) were it will then close down the injector openings, turn the A/C back on and reopen the EGR if it is required at that time.


CORRECTIONS; (errors due to typing too quickly) #1 - "allows the A/C unit to come back on. The ECU is designed", #2 - "the ECU will sense the throttle plate opening", ADDITIONS; #3 - If you were in cruise control before you "accelerated, when you lift your foot the cruise control re-assumes you wish the past setting and take over again as well. #4 - Newer cars also now "shut down" the power steering pump as well when acceleration is asked for.

My 2014 express does this as well, but it didn't for the first year and a half. If that is normal, I have even less respect for Chevy and it was already low due to the buyout (government motors= GM). If 300+ HP is insufficient to run the a/c, power steering and acceleration, then some more engineering is clearly necessary (I am a mechanical engineer myself). I think something is wrong with this sequence or with the dampers in the HVAC routing system that causes these issues. I'm already not pleased with the van to begin with because I've had to replace steering and brake parts every 30000 miles (more often than tires!) and the warranty won't cover them. If tie rod end and brake piston failure in 30000 miles is "normal wear and tear" for a $65000, 2500 series vehicle, I'll be buying Ford from now on.

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