99 suburban dual air issues

[jschmelzle]

I'll try to make this as short as possible. This is a rear ac truck. Ac Was never right in this truck in the 10 years I've had it.. cooled but not very well. Compressor started to come apart. Shrapnel in lines. Everything is new execpt front evap. Including lines. Evap was flushed thoroughlyVacuum pulled for 4 hrs held for about 20. Charged 3.9 lbs. It was 85 degrees the day I finished it. Low side 45-50 high side 275ish 56 degree air at idle. Drove it for 30 min was very happy with results would hit 52 on the highway. Next day was 98 outside took it for a drive. Air wouldn't get any colder than 68 on highway. Hooked up gauges .low side 80 high side hit 475 before I shut it down. New fan clutch and a furnace fan blowing on it 75/420. 68 degree air.. high side will drop to 350 if I turn rear air off. Any advice would be great!

[Cusser]

Hmmmmm - we've had 1994 Suburban and and 2005 Yukon Denali XL both with rear AC, bookending your 1999, in Phoenix AZ and the AC worked real well in those. Yes, each had an underdash actuator go bad, and each eventually get a replacement compressor, but things happen when stuff gets used.

We actually bought the 1994 WITH a compressor leak (could see oil/UV dye on it) but still worked/no bad noise and had local mechanic replace that compressor.

The 2005 developed compressor "slugging" and would break the small AC belt, so I installed a new compressor myself. This 2005 had electric condenser/radiator fans.

Your 1999 has really high pressures, has anyone looked at engine fan(s)/or fan clutch if you have one? You state you added 3.9 lbs, that works out to 62.4 oz., and the stated capacity I see for 1999 Suburban is 48 oz. Did you use individual cans or a large container, or do you possibly mean 3.9 CANS and nor lbs ????
What does the underhood sticker say for capacity?

[GM Tech]

Most common issue when replacing multiple parts on a dual system suburban is that the OEM orifice tube is on liquid line from condenser out to right in front of "Y" to rear system. Here is where the problem occurs-- Most all new condenser purchased will have a brand new orifice tube in the line out at the outlet connection of the condenser. So you as a consumer, have to decide whether or not you need it. You see, the same condenser is used on both dual systems and front only systems- the worst thing you can do is have no OT in place, hence they sell the new condensers with one in it. The second worst thing you can do is to have 2 OTs in the system- which maybe you do--do you recall removing the OT in the condenser outlet since you already have one in front of the "Y" to the rear? I've seen it degradate the cooling ability you speak of..

[JohnHere]

Checking my refrigerant-capacity database for a 1999 Suburban indicates as follows: All engines with rear A/C, 64 ounces of R-134a and 11 ounces of PAG-150 with the original Harrison compressor. If the replacement is a Denso compressor, the refrigerant and oil amounts are the same except that it takes PAG-46. As previously suggested, check the underhood decal for the A/C specs, which would take precedence.

[tbirdtbird]

Wonder how this 4 YO thread popped back up....

[JohnHere]

Good catch, tbirdtbird. I didn't notice the date of the first post.

[tbirdtbird]

Did not want you to spin your wheels, John. Dave