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s-15 gmc ,,,

pull-do on Tue August 16, 2011 7:55 PM User is offline

Year: 1984
Make: gmc
Model: S-15
Engine Size: 2.8 L
Refrigerant Type: r-12
Ambient Temp: 101
Pressure Low: 60
Pressure High: 275
Country of Origin: United States

Howdy,,, help please, see if you confer.
Posted on another forum,,,
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Been an ongoing project for a while, I've had the truck since it had 24,000 miles on it, now it has 200,000,,,,,,,, I like tinkering with AC's , but this thing has kicked my hiney, since the first time I re did it. I think in the 25 plus years I've had this truck I've re-built the AC unit 3 times,,, this last time, which has been about 8 yrs ago, maybe longer, I replaced
1/ compressor (new delco)
2/ hoses
3/accumulator
4/ orifice tube
5/ low pressure switch
Did the normal work, pulled and flushed evaporator and condensor, put it all back together, pulled a vacuum, looked for leak down, none happened, so I pulled the vacuum for about 3 hrs. and filled with , what I thought was the correct amount, r-12, by weight on the cans.
So here's the bottom line, all two or three times I've done this job, the best I can get out of it is 48 degree on the center vent, amazing to me how consistent this happens everytime.

This rebuild has been on for a while now, and the cooling or lack there of now, is getting pretty bad, I've added some more freon through the years hoping that might be the answer, not much, just trying to get the "feel" right on the inlet and outlet of the evap, no success,,,,,,,,, oh yeah, I thought one time it was the heater core getting me, I opened up the box, and the door was shutting off all the air flow past the heater core,,, I was sure hoping that was the problem, but nope.

I fixing to work on it again, way to hot here in Houston,,, checked it the other day, had 60 psi on the low side, 275 on high side, heat of the day, about 97 to 100 degrees here, everyday, high humidity also,,,,

Any ideas what I can do different that I haven't done,,,, besides carrying it to a shop,, I hate giving up on it,,, I had a '83 s-10 before this one and it'd run you out of the cab it was so cold,,, got enough r-12 on hand to do the job again,, just like to get it right this time. I always suppected the condensor but had no way of proving it, I do have a thermal gun now and I shot the condensor and it read 165 degrees all the way across but that doesn't tell me anything in particular, maybe one of ya'll can tell me.

Thanks for reading sorry for the rant, but I wanted to give all the info I could.


2nd post on same forum
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OK with all being said,, do ya'll think these pressures being put out by the compressor that I posted,,, 60 low side, 275 high side,, is the compressor still "healthy",, oh yeah, I've got a new fan clutch on it also.

Thanks for the replys

JJM on Tue August 16, 2011 11:46 PM User is offline

Are those pressures at idle or 1,500-2,000 RPM? Your low side pressure is very high.

Exactly how much R-12 and oil was added?

What orifice tube did you use? Did you lube the O-rings before installation? Did to OT click into place?

If the 165F temperature reading as at the very top of the condenser, at 275 PSI with R-12 that is what I'd expect. Question is what is the temp of the condenser inlet and outlet, so we can get an idea of subcooling. Also, run your IR gun from the top of the condenser, left to right, and go down slowly (following the coils). Temp should drop gradually. Any cold spots are a sign of a restriction?

I know the heater door closes, humor us and clamp off the heater hoses for 15 minutes and recheck vent temps.

If I'm reading correctly, you pulled the evaporator... did you seal it up properly with new sealant?

Joe

When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com



pull-do on Wed August 17, 2011 12:55 PM User is offline

Quote
Originally posted by: JJM
Are those pressures at idle or 1,500-2,000 RPM? Your low side pressure is very high.

those are idle pressures



Exactly how much R-12 and oil was added?

I weighed the r-12 by what the can said it held, didn't have a scale, this was a while back, but I think it was 6 ozs of oil,,,, whatever the book said, is what I did,,,,,,, since then, about 10 yrs. ago or more, I've added freon trying to get it to cool a little better, even the first time the duct temp was 48 degrees like I posted.



What orifice tube did you use? Did you lube the O-rings before installation? Did to OT click into place?

Don't remember the tube color, but it was the one called for,, yep, lubed the o-rings,,,,, click in??? I don't remember honsetly.



If the 165F temperature reading as at the very top of the condenser, at 275 PSI with R-12 that is what I'd expect. Question is what is the temp of the condenser inlet and outlet, so we can get an idea of subcooling. Also, run your IR gun from the top of the condenser, left to right, and go down slowly (following the coils). Temp should drop gradually. Any cold spots are a sign of a restriction?

OK, I'll check



I know the heater door closes, humor us and clamp off the heater hoses for 15 minutes and recheck vent temps.

Done that already a while back, just forgot to post it up. Oh yeah, no significant change



If I'm reading correctly, you pulled the evaporator... did you seal it up properly with new sealant?

I did the case and outlet and inlet tubes,,,, but it's been so long I can't remember if it was sealed internally around the edges of the coil.

What about those compressor readings, 60 and 275,,,, compressor still good, I would think so, but would like to have an opinion.
Thanks,
Paul



Joe



When considering your next auto A/C purchase, please consider the site that supports you: www.ACKits.com

JACK ADAMS on Wed August 17, 2011 3:25 PM User is offline

Sound like you may be in Normal a/c mode, check your Fresh-air/Recirculation door to make sure it is fully functional. This is a vacuum operated door motor. one is located on the passenger side kick panel and the other door will be in the hood cowl.. Hope this helps and good luck.

Dougflas on Wed August 17, 2011 6:49 PM User is offline

Don't know if I missed it but have evr changed the cooling fan clutch? You may want to mist the condenser with a water hose and see if the pressures drop like a rock.

mk378 on Wed August 17, 2011 8:14 PM User is offline

I'd agree with Dougflas, declining performance over a period of years is likely the fan clutch getting tired and the radiator + condenser clogging up with dirt.

Since you're using R-12, install exactly the factory amount and see where your pressures are. Poor condenser performance leads people to undercharge a system when they see the high side going up higher than it should.

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