2002 GMC Sierra ac not working correctly

I am having issues with my trucks ac. I filled it up with Freon after it blew hot. And it blows cold for a few days then stops, initially found that the low side valve was stuck open so it might have leaked out. I replaced the valve and filled it again and it did the same.

Found that when I filled it up after fixing the valve the compressor would not shut off so we took some Freon out to get it to switch on and off because the line was freezing.

I’ve also replaced the orifice tube.

Any clues?

Was a vacuum pulled on the system to remove any air/moisture?


We emptied Freon with a machine at my dads job, so it does vacuum it

How many inches of vacuum did it pull, and how long did you hold it there? Also, if you didn’t replace the receiver/dryer, you should have.

Not exactly sure, when we emptied it, we let it vacuum for 30 minutes

You need to hold 25" of vacuum for 30 minutes to vaporize all non-condensables.

You need one atmosphere, (29.92" Hg) to evacuate an AC system.


I’ll have to replace the accumulator, might try vacuuming it out again, and seeing if there is a leak also. Cause I keep having to put Freon in. Compressor doesn’t make any unusual noises and cuts off and on so I don’t think that would cause anything

Tester is correct. I should not post after my second martini.

What did the orifice tube screen look like?


It was pretty dirty, some small pieces of something on it

That’s too bad.

That’s an indication that the compressor is failing.

The only mechanical part of the AC system.


From it being dirty? The orifice tube didn’t look like it had any metal shavings on it or anything, more like dried about oil

Since your dad seems to be equipped with tools . . .

inject some uv dye through the low side, while the engine is idling and the ac compressor is engaged

Eventually, an ac component will turn green . . . and that is the cause of the leak

I got some Freon with sealer/uv dye in it and I didn’t see any green anywhere besides the low side valve where I put it in at

are you using the correct black lamp and yellow lenses to look for the leak . . . ?

Keep in mind that some components aren’t easy to see . . . such as the evaporator and the back side of the condenser, which faces the radiator

Look up automotive AC black death in your search engine.

That’s how it starts.


Yes, we used it