suburban a/c problem stumped please help

[johnwas]

first working on 1999 chevy suburban 5.7 with dual air

heres whats been done so far


New
rear evaporator
expansion valve (rear) (auto zone)


all lines from rear to the front where they connect to the main lines under hood
(eBay special made rubber barrier hose)


reman compressor (eBay cheapest )
new accumulator (came with compressor)
new orifice tube (front ) (napa)




ac was a little weak last year so when a ahead and replaced compressor as i had multiple leaks
in the rear lines and destroyed rear evaporator getting them off expansion valve was OK but got it
a part and was only $10 so that's new


compressor was filled with 2 oz oil and turned by hand 12 time before install per instructions with compressor

now installed all myself blew all lines out with shop air (triple filtered and dried )
then with some line cleaner for when compressor goes bad .


Added the 10 oz of oil ( book calls for 11 oz )


Was vacuumed to 330 micron over night


added 4 cans 134a walmart cheap stuff
1 can first start 134 + dryer + oil
never lost vacuum at any time before 134a put in


now my problem
ac is warm at idle at vent ( 70 f ) out side 90f
and (60f) going down road


gauge readings with both front and back on high
low 40 psi / high 200 psi


with front high back off
low 30psi / high 160 psi


lines dripping like crazy
air is blowing hard and strong from all vents
recalculate button in on


when you shut ac off pressure equalizes smoothly and quickly
and yes I have had ac tech look at and hes scratching his head too


heater core lines are pinched off too


please help thanks

[mishalah]

Are your low side readings at idle or with the rpms pushed up to approx. 2000? If at idle speed than it would explain the difference from when driving. That's pretty normal from what I experience with most cars, but I'm not sure what the differential is supposed to be between in the driveway vs. on the road. I think the 30 degrees on the road is good, but the resting should probably be a little closer to the 30 degrees than only 20 degrees.

The 40 on the low side at idle might be ok, but at 2000 or so rpms it shoud definitely be more like 30. Normally, i'd say your a little low on the 134 charge, but I seldom use R134 any more so it could be normal. If you are bringing the rpms to 2000-2500 and the low side is still at 40 then yoou do need a little more juice. How's the cycling of the compressor? At 90 ambient it should probably run most of the time with the settings all on max. ....especially if the windows are all open.

[Cusser]

I'm agreeing with the above post. Personally, I would have used a NEW compressor (but you've already done yours), and added just UV dye and R134a, no "R124a + drier + oil". So let's say 4 cans of 12 oz. plus maybe 10 oz. in the "super" can gives 50 ounces R134a, if every last gram got into the system. http://napabeltshose.com/news/index....&show=newsitem states that 64 oz. go into the system, think you're at least 1/2 a can R134a low.

I added 6 cans to fill my '94 dual-air Suburban a few months ago after I installed my new compressor and accumulator, nice and cold in Arizona. Run the pressures at 2000 rpm after a few minutes of operation and post those.

One should always have the AC on in the rear on dual air systems when the front AC is on, to vaporaize the refrigerant so liquid refrigerant doesn't make its way back to the compressor, which will cause its steady demise.

[j cAT]

with the air temp at 90def f you should be getting 250 psi on the high side ...with the info you listed I would check the newly installed orifice tube for more restictions ...

adding a few oz more of refigerent oil PAG 150 will not damage anything , too little will....

the lines with a failed compressor should be flushed out ...need special equiptment ...debis gets to the orifice tube ..don't take much ...so if it is dirty you must have this cleaned properly and hope the new compressor did not get damaged ...

[brcidd]

Most common mistakes made when dealing with C/K trucks and suburbans

#1 Condenser is plumbed backwards-- condenser has same connectors on both ends-- is your compressor feeding the top of condenser? as it should--

#2 system has 2 orifice tubes- one in condenser and on in-line just beyond the "Y" You have a rear system-- there is no OT in outlet of condenser-- some condensers come with OT already installed- make sure you DO NOT have one in your condenser and you do have one in line just beyond the "Y" split to th rear system

[cris2004]

I had a similar problem years ago after replacing parts with my 98 . The pressures were OK but the cooling was not. It was a result of too much oil in the system, not allowing proper expansion I guess.
My solution was to crack the fitting in the rear low point of the system, near the exhaust, and allow oil only to seep out, then tightend. I suppose this is risky if you're sure on the oil, It work great in my case.