AC acting weird...

[jwlael]

Ok, I have a 2000 GMC sierra extended cab 4x4. 106k miles. When I got it, it was low on Freon and I charged it to the right pressure levels. AC blows cold and works great.

Now lately as im driving you will hear a pretty loud woosh sound. The high pressure relief valve is letting freon out at random times. I took it to my mechanic and he took the orifice tube apart and took the filter out. It was mostly clean with a couple of small metal pieces about 5mm long and shinny. He put a new one in, and refilled the ac system and added some oil. Works great as it did before very cold.

This only happens when you drive the truck, when in park it doesnt activate the pressure relief valve. I reved the engine to 3.5k rpm and nothing happens, pressure stays good. Fan works good, I have good air flow.

Could the compressor might have been sticking or something? Should I run it with the fresh oil and charge and see if it helps it along? Ive never had a vehicle do this before, and still have working AC.

Thanks!

Joe

[DeltaP]

Need to diagnose this with manifold guages attached to system and an experienced tech at the helm. Pressure relief valves seldom fail and they're set to relieve press in excess of 400psi. The fan keeps the head pressure down and you say it's working. But is it turning on and off at the right pressures? Another possibility is a restriction in the system most likely the condenser. Hondas were well known for this. GM's not so much unless an improper compressor/ component change was done in the past.

[jwlael]

The relief valve is going off at like 40 psi on the low side. The pressure will go up like its building up. The ac blows very cold. I had it at the shop and they had gauges on the high side and it was fine too. They ran it at idle for a long time and it never went off, its only when you start driving the truck that you'll get the sound of the relief valve letting freon out. The Ac system has never been replaced or messed with, when I took it to the shop they replaced the orifice tube on it. Could the compressor cause this even though its working? I find it strange that the ac works yet its kicking out freon when you drive it.

Another thing is im not sure (im not a super mechanic) but it looks to me the condenser is built into the radiator? I cant tell.