1998 suburban A/C problem, need help.

[fyescas777]

I have 1998 suburban 2wd, 1500, regular gasoline with rear A/C. I replaced the front evaporator , compressor, and the orifice tube. I also flushed the whole system with nitrogen and flush fluid. BUT the AC still does not cool, very little. Air coming out is at 70 F, suction pressure is at 55 psig, and discharge pressure is at 305 psig. What could be wrong? I added 3 lbs of refrigerant and stopped because of high head pressure, unit takes 4 lbs. Ambient temp was around 95 F. And I also pulled a vacuum for about 45 minutes, I know it is no longer leaking. NOTE: reason I replaced compressor and evap was because both were leaking.

[brcidd]

You may have flush left in system- purging with air and vacuuming does not guarantee you got it all out- that's why I only flush with refrigerant. I would never put anything into an a/c system that I don't want to take the chance it won't come out.

I also never flush for a leak--

With less than spec refrigerant in there and high suction and high discharge pressures- you may have air in the system as well-- there is some sort of non-condensible in there-- either air or flushing agent- which causes high suctions and high discharge pressures and rotten cooling.

[j cAT]

Originally Posted by fyescas777

I have 1998 suburban 2wd, 1500, regular gasoline with rear A/C. I replaced the front evaporator , compressor, and the orifice tube. I also flushed the whole system with nitrogen and flush fluid. BUT the AC still does not cool, very little. Air coming out is at 70 F, suction pressure is at 55 psig, and discharge pressure is at 305 psig. What could be wrong? I added 3 lbs of refrigerant and stopped because of high head pressure, unit takes 4 lbs. Ambient temp was around 95 F. And I also pulled a vacuum for about 45 minutes, I know it is no longer leaking. NOTE: reason I replaced compressor and evap was because both were leaking.

I agree you have some non refrigerent in your system this is why the low side is too high ...the high side appears good..

what happens is the oil absorbs these non refrigerents and it does take some time for these to boil off under a high vacuum..one way to test if you have a leak or still have these non refrigerents is to shut the vacuum pump off and see if it holds the same vacuum for a time...then you will know if its ready to charge...

only put in the spec wt...where you live you will damage the compressor and other ac componets...best error on lower amounts than too much,,,,.

on your air temp at the discharge vent being 70deg F,,well if you live now where its 110deg f the 70deg f coming out sounds good..

[fyescas777]

The reason I used flush solvent was because the old oil seemed very contaminated, it had green dye, and the red gunk (leak sealer) and smelled really bad. I will try to flush the whole system again using only nitrogen and perhaps some refrigerant. Thanks for the advice.

[j cAT]

Originally Posted by fyescas777

The reason I used flush solvent was because the old oil seemed very contaminated, it had green dye, and the red gunk (leak sealer) and smelled really bad. I will try to flush the whole system again using only nitrogen and perhaps some refrigerant. Thanks for the advice.

I would also replace the oil again ..I don't use or recommend these sealers...most have problems ..

[spinne1]

You might still have a leak in the rear system. You did not mention the rear system having anything done to it. Did you check it? Is your rear expansion valve clogged or malfunctioning in some way?

I had to redo my 95 AC, which meant my condensor, compressor, several lines, all orings, the expansion valve in the rear, the accumulator, and orifice tube. It works good now but is not perfect. The front blower motor isn't strong enough for such a large space, but that is a design flaw.

[wendypape]

I too have the same problem in the wife's burb. We bought in used in great shape, but put almost $1000 in to get air conditioning fixed and it's still not working! She loves it, but between that and the door lock issue, she's not having fun! Nice to know it's not just us though....hope to learn some things here to try and get to the bottom of it's issues!

[miked79928]

Originally Posted by wendypape

I too have the same problem in the wife's burb. We bought in used in great shape, but put almost $1000 in to get air conditioning fixed and it's still not working! She loves it, but between that and the door lock issue, she's not having fun! Nice to know it's not just us though....hope to learn some things here to try and get to the bottom of it's issues!

Off topics, but in regards to the door lock issue does the vehicle have the keyless entry option? My 99 suburban had issues with the door locks and it turns out the keyless entry module was messed up. Might be worth looking into...