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Air Conditioning Works While Parked But Not While Driving, Why?

1994 T 600 air quits working after you start driving it works good sitting i have replaced everything

Answer this question I have this problem too

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'''Both answers are good. I would check the heater lines coming out of the cab on the firewall and see if they are hot. You will have a line coming from the engine to the firewall then one coming out and going back toward the sleeper, if that line is hot that will be your problem. That is why most trucks have a faucet type shutoff valve on these lines to stop the flow of coolant in the summer time.

Or the system could have too much Freon in it causing the head pressure

to go up and kick out the compressor till the pressure comes down then allowing it to kick back in.

You also have a low pressure switch so if the Freon pressure drops too low due to a leak you won't burn the compressor up.

The last two involve hooking gauges to the system and someone who knows how to read them. 'italic text''

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not sure what you mean by "replaced everything", but you might check your heater control valve, mine failed on me last year and the ac couldn't keep up with the heater. may not have enough heat in the heater while parked. to check, run the fan without the ac on and the control valve in the coldest position. the air coming out should not be much warmer than the outside air.

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Could be because the compressor starts short cycling due to suction pressure being too low once the condenser pressure drops from the increased airflow. If so, you'll need to add refrigerant.

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Not sure what replacing everything means but I have seen the dryer getting stopped up cause that because the freon can not flow like it is suppose but u should let someone hook gauges to it and ck pressures against outside temp.

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My friends 2001 KW T-800 was doing the problem as the persons who started this post. Turns out on his truck, he had a bad expansion valve.

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condensor might be freezing up

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Have you checked you cab filter.

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michael will be eternally grateful.
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