( 04 suburban with rear air) Hi Guys, my AC has been working fine until.a week ago. The compressor took a crap so I removed the old one and the next day I replaced it. ( I had left the lines exposed over night ) I ran the evac pump for vacuum for an hour and it held at -29. Perfect..I put in a can of 134a with oil ..no problem. Put in a can of 134a and now it started to blow cool. When adding the 3rd can of134a the pressure spiked ok the low to full and air went warm. I shut the truck off. Google symptoms and it said it could have been over charged..but it wasn't because it takes 48 Oz. I only had about 26oz in. So after no luck fining answers I said" I'll just start over from scratch. Opened it up( yeah yeah) at the pump. Went to pull.a fresh vacuum.and now it would only go to -9. Tried multiple pumps and still no luck getting past-9. So, I was thinking maybe I damage and internal seal? So I removed the lump , exchanged it and put it on. I replaced the orifice tube while it was open. Pulled a vac and still -9. Do I have a clog somewhere? I hooked my air compressor to it and locked in positive pressure and it held it. But yet I can get a strong vacuum. I read that being I had the system open for a period if time( over night) that the accumulator needs to be replace. Gould that alone cause poor vacuum?? Please help !

 

The desiccant may of absorbed so much moisture that your pump is going to have to be on it for all extended period of time to pull all the moisture back out of the desk and. You could also replace the desiccant and I'm not sure where they have it in one of those systems.

 

1) A clog will not prevent the system from pulling a complete vacuum - there’s either a leak somewhere or the vacuum pump has a problem.

If the compressor is the only place where you opened the system, remove the lines, plug them in a way to ensure they’re sealed (rubber corks work well) and try to vacuum.

If it still doesn’t pull a complete vacuum, and you’re sure there’s nothing wrong with the pump, plug the lines for the rear evaporator and attempt to vacuum the front half of the system.

If it still doesn’t pull a complete vacuum, try to rig the system to only vacuum the rear half.

If you can pull a vacuum on just the front or rear, the opposite side of the system has a leak (ex. the front pulls vacuum but the rear doesn’t means the rear has a leak).

-Make sure you lubricate the seals with clean PAG AC oil.

2) The desiccant used today does not allow for moisture removal during vacuum. It may give up a little but retains most of it. If it’s been exposed to atmospheric pressure for 24 hours, it’s no longer useful as a drying agent.

It’s located in the accumulator.

 

Most compressors I've bought come precharged with compressor oil. Adding a full charge of oil on top of that, plus any oil still in the system from before your compressor was shot, could be causing issues to where you can't hold a full refrigerant charge.

The other thing is that when your old compressor died - was it catastrophic, or just a clutch failure? I ask, because when a compressor dies, it can send metal and stuff through the rest of the system, causing it to need to be flushed. Unfortunately, modern condensers (the coils in front of the radiator) have such small passages they are difficult or impossible to flush. Orifice tubes can also clog. As others have pointed out, having the system open for a day also likely led to the dessicant in the accululator/dryer being ruined.

Last time I replaced a compressor on my C1500 for a non-clutch failure, I replaced the accumulator and the condenser - I bought a 4 Seasons kit that had compressor, condenser, accumulator and orifice tube.

Now, NONE of the above explains not being able to pull a vaccuum to near -30. Are you hooked to both the high and low side ports, with both sides open while pulling the vacuum?

 

Agree: we need to know exactly what was wrong with the compressor.

If only the AC clutch failed, then I'd agree to replace the compressor only, but I wouldn't have left it open to atmosphere overnight. Same if there was a compressor front seal leak.

If the compressor seized, I'd replace the condenser, accumulator, and orifice tube, and backflush the high pressure lines with solvent.

We had a 2005 Yukon which developed compressor slugging and broke the AC belt several times, but still cooled otherwise, so I gambled and installed just a new compressor, and I won that gamble.

When the compressor on my 2004 Frontier seized, I replaced the compressor, condenser, and drier, and backflushed the high pressure lines with solvent to fix.