A/C Issues STILL ONGOING

[armyhockeynut]

I continue to have issues with the A/C unit in my 2004 Chevy Silverado 2500HD. This has been an ongoing issue for several years and numerous trips to the repair shop. Everytime, someone thinks they "figured it out", it works and then returns to the same old thing. First off, the issue is not that it needs to be "recharged" This is a common repsonse, but that has been check and rechecked and all in order. No leaks either. The basic problem is that the A/C will work fine as long as the truck is maintaining a decent RPM. If we hit heavy traffic or stop and go city traffic, the a/c gives out and never returns even if we get back up to a prolonged period of normal speed. When we are towing the camper it is worse. Friday and yesterday the A/C would not work at all. As we drove I had a volt meter in the cigarette lighter and it was reading around 13.87 when I would turn on the a/c it would only drop to 13.77. Aa most know, yesterday was not a day to be without A/C here in Virgina.
This morning, I drove the truck to the train station and the volt reading was 14.45 and the a/c was blowing ice cold. In thwthe afternoon the a/c blows cold on the ride home too. So I am at a loss.
My gut says that the A/C is not getting the required power it needs to run properly.

Input please!

[Engineer9860]

Check the air gap between the A/C compressor clutch, and A/C compressor pulley. If the gap is at the maximum limit a low voltage may not be creating enough of a magnetic field for the electromagnetic coil to pull the clutch in.

[ScottG]

It sounds like the clutch fan isn't locking up anymore.

[ryhed]

Anyone put stop leak in it? it makes the inside of the refrigerant lines smaller and it could make it quit working efficiently. I would probably buy all new lines a drier and clean the condenser. Make sure your fins are clean and straight on the condenser. Is the blend door operating correctly?

[JRS___B]

Is the compressor engaged when the unit is not performing?

I can't believe no one looked to see if the compressor is turning or not.

If it turns out to be a bad clutch, or wiring to the clutch, or a relay for the clutch, then you need a new mechanic as well.

[Dr_Quick]

I do not think that the voltage is a problem. Some things come to mind. If everyone thought that system was low on refrigerant and added some, an over charged system can shut down due to high pressure. Could be that pressure switch is bad and causing system to shut down, when in traffic and lower air flow would cause pressure in system to rise. Not sure of his one, but when in traffic, temperature of engine will rise. Possibly since AC running at the time could cause computer in vehicle to shut down AC to "save engine" from over heating, due to extra heat proceeded by AC system.

Has anyone tried connecting a computer to OBD port, and road testing the vehicle under the conditions that you describe? This could possibly help to view system pressures and temperatures to see if they are normal, or excessive.