Suburban Front/rear A/c Question

[ga1990]

So the compressor on my 2003 Suburan LT started making the appearantly common vibrating type noise, so I replaced it this weekend. I replaced the compressor, accumulator and orifice tube. At 1500 rpms my low side pressure is around 42 and my high side is around 250. Everything seems to be functioning fine, however my rear air blows at 57 degrees, and my front is only blowing around 67 degrees. It was around 95 degrees outside when I took these readings. It may or may not have had this issue before I completed the work, I never checked it. The one concern I have is that it only took 2 cans of freon (24oz.) to reach these pressures. Per my manual it should have take 4 cans or 48 oz. When I started to put the third can in my pressures went way high and I had to remove some.

 

I balanced the oil in the compressor, adding the same amount to the new (after draining) that came out of the old one, and then I added 2oz of oil to the accumulator, which seemed to be the right amount per the manual.

 

What could be causing the difference in temps? Is it normal for the system to take only two cans of freon? Thanks for the help.

[Jsdirt]

Did you charge into a vacuum? If not, that's your problem. Air doesn't play well with refrigerant.

[ga1990]

Sorry, I should have posted that, I vaccumed the system down for 30 minutes and the vaccum was holding right between 28-30 when I charged it.

[Doug_Scott]

You have to put the measured amount of refrigerant back in. If it calls for 48oz of refrigerant then that is what you put in. You also have to make sure you have enough air going through the condenser. I have used a garden hose when I could not supply enough air when the ambient air temp was high and the humidity was high as well.

Sometimes water running over the condenser will be the trick.

[ga1990]

I tested the temps while driving, so there should have been enough air movement. As far as the amount or refigerant goes....I added about a half of a third can and then my pressures started getting way too high...low side was around 60ish and high side was around 400ish and the compressor started kicking off, I'm assuming because the pressure was too high. So I removed some freon until my pressures were back to normal. Can you think of any reason I would be getting "normal" pressures with only half the system's capacity of freon?

[Jsdirt]

You say your charging with cans ... it is possible that some air got in while changing them. If I use cans, I bleed the lines after piercing the fresh can each time by cracking the line on the gauges & letting it spray for about 5 seconds. That ensures no air will be sent into the system.

 

Another possibility is a blockage in the system somewhere. If the old compressor grenaded & sent shrapnel through the system, it will clog just about everything, & the whole system will need a flush. Even if just a few shavings were released, they will plug up the orfice tube if enough of them build up. That will make pressures go sky high.

[ga1990]

Thanks for the reply...I did purge the line with each can...not for 5 seconds, but just long enough that I felt it was only freon coming out of the top. Maybe that wasn't good enough? The old compressor was still working when I removed it, and the old orifice tube didn't have much on it, so I didn't feel a system flush was necessary. Now I'm wondering if that should have been done.

[Jsdirt]

Were these just 134a cans, or did each one have oil? If you didn't flush & each can had oil, that;s going to be an issue.

 

Sealer is even worse - I don't use sealer unless the vehicle is destined for the boneyard. If you have the system open for any length of time the sealer will harden ... and at that point it's easier to replace everything than to try flushing that crap out.

[ga1990]

Just plain 134a, these right here: http://www.autozone.com/autozone/accessori...mp;viewAll=true

 

As far as I know there's never been any sealer added to the system, but I've only owned the truck for the last 3 or 4 years...but as of now it only has 55,000 miles on it, had 32,000 when I bought it, so I doubt it had any AC service done, but I guess you never know.

[Richard T.]

I replaced my AC hoses and my dryer I ran vacume on the system for an hour, but when I go to charge it with cans of freon it only takes bout half of what it should before the pressure on the gauges go above normal. The gauge pressures 60 and 175, the question is what could be keeping my system from taking full charge?

 

Some side information, the rear AC runs cool and the front AC runs warm. My front evaporator inlet line is very cold but the outlet line is warm. Also the compressor is a little noisy. According to the car manual normal pressures are anywhere from 15 and 125 to 75 and 350 psi.