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1999 GMC Surburban Expansion tube replace

robsd on Wed June 11, 2008 10:50 AM User is offline

Year: 1999
Make: GMC
Model: Surburban
Engine Size: 350
Refrigerant Type: 134
Ambient Temp: 85
Pressure Low: ?
Pressure High: ?
Country of Origin: United States

It's been working fine, I had to replace the low side schrader valve a while back, didn't lose much 134, I just replaced it with a kit from Walmart...with the little gauge. Currently the gauge reads normal. When you turn it on the low side tube on the compressor gets really cold, with our humidity down here even a layer of frost until the engine warms up. But after a while now if goes less cold. Vent temp about 60-65. Looking at the engine I found what I think is the expansion valve on the left on a line just before it goes into the condensor. It's really cold on one side, then warmer on the condensor side. This thing may have 2 valves? The rear air is the same as the front air as far as temps go. Everything else is OEM. Do you think this valve is clogged up?

Any suggestions?

Thanks,
Rob

GM Tech on Wed June 11, 2008 11:29 AM User is offline

If you have rear air on your Burban- which it sounds like you do--- then there is not supposed to be an orifice tube (OT) at the condenser outlet like the front air only systems have--- the OT is to be right after the "Y" in the liquid line at the frame rail -- My guess is that since you say it is cold at the condenser outlet- that some jack ace mechanic has you now running with two OTs- not a good situation- although highly possible to make that mistake- so open up the connection through the passenegr turn signal opening and see if yu have an ot in there---

Might as well be sure you are plumbed correctly while you are at it-- the hose from the compressor MUST plumb into the top of the condenser- the bottom condenser outlet must feed the "Y" split-- this is another ingenious mistake waiting to happen on the condenser- since both ends have the same connection threads.......

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The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

mk378 on Wed June 11, 2008 12:05 PM User is offline

Yeah the high side line should not get cold until AFTER the Y connection, and then only for the front side.

robsd on Wed June 11, 2008 2:53 PM User is offline

That may be near the Y connection. The line that I believe hold the OT is on the passenger side, just inside of the tire on the frame. I scanned some other posts and the line has the 3 crimps in it. We've had the truck since it was new and no one has touched the AC. I thought I read in som earlier posts that the Burb has 2 OT.

But all this aside, would a stopped up OT cause this problem? I guess I really need to put some gauges on it because it it is plugged then the pressures might show it.

Thanks,
Rob

robsd on Fri June 13, 2008 9:24 AM User is offline

It is to the rear of the Y connection, condensor, Y then OT. I just made a quick look but I guess the other part of the Y with no OT goes to the rear.

But are my problems symptons of a restricted OT?

GM Tech on Fri June 13, 2008 9:36 AM User is offline

You are probably still low on refrigerant- does your compressor look like this:

Belly Leaker

-------------------------
The number one A/C diagnostic tool there is- is to know how much refrigerant is in the system- this can only be done by recovering and weighing the refrigerant!!
Just a thought.... 65% of A/C failures in my 3200 car diagnostic database (GM vehicles) are due to loss of refrigerant due to a leak......

robsd on Fri June 13, 2008 9:53 AM User is offline

It's hard to say, I can't recall exactly and it's at home. The lines are all different, my gauge connections are all on top.

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