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Yukon's future?

72hotrod on Sun August 17, 2008 3:46 PM User is offline

Year: 2003
Make: GMC
Model: Yukon
Engine Size: 5.3
Refrigerant Type: R134a
Ambient Temp: 92
Pressure Low: 40
Pressure High: 200
Country of Origin: United States

The compressor started making bad noise, so quit using A/C immediately. Got new 10S20F, O-tube, accumulator, TXV, in-line filter, condenser, POE, O-rings, sealing washers,and Nylog. Upon teardown found large mass of ground metal at O-tube and plugging rear TXV. No blackness at all, clear oil(w/dye).

Flushed rear evap with lacquer thinner and replaced TXV. Flushed rear lines (disconnected) in-place with mineral spirits. Removed front lines and flushed. Flushed front evap in-place and replaced condenser(W/1 oz POE). (Blew all items with 120 psi with blowing chuck (drilled for most flow possible) until there was no more smell, over 2 days time.) Drained shipping oil from compressor, flushed twice with POE, loaded w/5oz POE, installed and connected lines. Installed in-line filter, O-tube, lines and accumulator(W/5oz POE). Rotated compressor numerous times to move oil. Pulled a vacuum that leaked down in 15 mins, so added a few ozs refrigerant and found and fixed 2 connections not tight. (My apologies to any penguins.)

Added dye and vacuumed several more times holding vacuum each time. Ran engine for heat, vacuumed again for an hour, held overnight with needle pegged at full vacuum. Vacuumed again for 30 mins. next morning and charged 36 ozs. as liquid into high-side, which went in pretty quick. Hooked up last can and charged as gas into low-side until it wouldn't go(half can), then started engine to finish.

With 92* amb, very high humidity, vehicle opened up, rear air off, front air temp set lowest, and blower highest, got center vent temp of 71*@500rpm(idle):LP40-HP200, 59*@1500rpm:LP45-HP235, 59*@2000rpm:LP44-HP240.
W/rear air on:
72*@500rpm:LP68-HP250, 67*@1500:LP62-HP275. No 2000rpm test.

Now my questions are:
1-The system calls for 43.2oz refrigerant, and by the can I installed nominal 48oz but with some loss at purge for can change(minimal?) and some residual in hoses afterward. Do these numbers indicate a charge within tolerance? I never got frost on suction side (lots of condensation), and really couldn't be sure by the hand how different the temps were in and out of front evap (seemed the same). Front evap drain was pouring tons of water (rear as well).
2-What can be done to guard against a future failure like this in this system?

Thanks to all who contribute to this forum, and AMA for sponsoring.

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The Worst mechanic I know, but the Only one I use, is Me! Watchout!

72hotrod on Mon August 18, 2008 8:34 PM User is offline

Drove the Yukon to work today to see how it works, it's the wife's truck so I needed an excuse. It was cooler weather as there is rain in the forecast and overcast skies. Well with 85* weather and the A/C set on re-circulate, the digital thermometer in the center vent showed some temps as low as 33* at times. Since I don't really know how to adjust the A/C controls for best all-around comfort, since I never drive it, I was pleased with the cooling. Before I tried re-circulate, it was still cool in the vehicle with vent temps dropping to about 49*.
Now if I can figure out what killed it before, I might feel better about things. Maybe the PO never had it serviced and lack of oil migration due to natural loss of refrigerant was enough to eat the compressor? Maybe there was compressor slugging? Maybe there was compressor washout by refrigerant coming from an under-utilized rear air unit. There was a good bit of oil in the two evaporators and the rear lines, but since I really didn,t recover it, I have no measurements. No signs of leaking dye before I tore it down.
Maybe I'll never really know, so what is the best plan going forward to maintain this machine?

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The Worst mechanic I know, but the Only one I use, is Me! Watchout!

TRB on Mon August 18, 2008 9:59 PM User is offlineView users profile

First you need to get the correct charge in the system. R134a systems need to be charge as close to OEM specifications as possible!

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