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Newbie errors in POA system

highperf4x4 on Tue July 07, 2009 11:03 PM User is offlineView users profile

Year: 1972
Make: GMC
Model: SierraGrande
Engine Size: 402
Refrigerant Type: 134a

Ok, I inherited my late grandfather's pickup a few months ago. A/C was not working and the belt was off the compressor. The bearing for the pulley on the compressor was locked up however the clutch would turn ok. The system was empty. I had it evactuated anyway (I probalby should have had it flushed but I didn't have that knowledge before I got to this website) I installed a new (reman?) compressor from Oreily's and a new dryer. I didn't put a vacum on the system (again, didn't have the knowledge) and I charged it with oil and 4 cans of 134. It blew pretty cold for a while and I thought I was in good shape for very little work and then it slowly quit blowing cold. I added a little more freeon and no help. After for looking for answers at the truck forums, I ended up here. I've read alot. I didn't even know what a POA system was before now and I still don't have solid grasp on it. I did however pull my POA valve and try to adjust the valve counterclockwise about 1/4" but I don't know if that's 26 psi or not. I read on here somewhere that someone named Mitch was adjusting them for 20.00. I might look him up on that. I'm going to pick up a vacum pump and a set of gauges and take a shot at charging it right but my question is this........ by not putting a vacum on the system beforehand and not flushing it, what's the worst that could have happened? Like I said, it blew fairly cold at first and then stopped. Could I have plugged something up?

Chick on Wed July 08, 2009 6:37 AM User is offlineView users profile

First, find and fix your leak.. There is a reason the refrigerant is gone, as it's not consumed like gas, next the proper evacuation procedure is on the tips and FAQ page of this forum, you must pull a vacuum and charge VIRGIN R 12 or R134a into the system, with the proper amount and type of oil. Don't add the magic in a can junk, you will ruin the new compressor.. Flushing the system of the old oil will remove the old oil and junk that you put in there.. Flushing procedures are also listed in tips and FAQ..hope this helps.

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

highperf4x4 on Wed July 08, 2009 9:28 PM User is offlineView users profile

I haven't been able to locate a leak. There isn't any visible evidence of one that I can find. No oil spots anywhere. I'm not sure why the system was empty when I got it. It may have been evacuated by my uncle. It hasn't had a belt on the compressor since it locked up on him 10 years ago and he can't remember what he did to it. The refrigerant that I put into it didn't leak out. It just quit cooling after a few weeks. I added a little more freeon to it just to make sure but then it showed overcharge on the low side. I don't know what the high side was showing becuase I didn't have a gauge manifold but I picked up a set tonight along with a vacum pump. The system is empty now as I pulled the POA valve and adjusted it. I'm fixing to put a vacum on it just as soon as I figure out how to do it! :-))

Edited: Wed July 08, 2009 at 9:30 PM by highperf4x4

highperf4x4 on Wed July 08, 2009 11:55 PM User is offlineView users profile

Ok, I pulled a vacum on it to negative 29 (all I could get with the harbor freight pump) and let it sit for an hour and it hasn't even wiggled so I'm assuming no leak. I will try to charge it tomorrow and post high/low pressures. I will have to find a thermometer for the vents though.

highperf4x4 on Fri July 10, 2009 12:41 AM User is offlineView users profile

This morning I checked the guages and I had still the full vacum so no leak. However, when I tried to charge the system I only got 2 cans into it and I started to get funky readings on the guages. Most notably, when I turned the a/c off the high and low sides equalized almost instantly to 100psi each and when I turned it back on I got 24psi low side and 125psi high side. What would cause that?

Chick on Fri July 10, 2009 5:49 AM User is offlineView users profile

24 low and 135 high? What was the ambient temp with those pressures, and how was the air coming out of the vents? Sometimes charging with cans takes a while after the system builds pressures, but with 24 psi low, should suck the refrigerant in..

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Chick
Email: Chick

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Freedoms just another word for nothing left to lose

highperf4x4 on Sun July 12, 2009 11:51 PM User is offlineView users profile

I don't know what the ambient temperature was but that was only about a half charge. When I noticed the low side jumping up over 100psi as soon I turned the compressor off with only a half charge on it, I decided to stop and do some more troubleshooting. I'm going to replace the POA valve with a CCOT. I've found someone locally that will take my POA apart and change out the guts and add a pressure switch to it for 50.00. Does that sound like it might be something worth trying?

Dougflas on Mon July 13, 2009 5:08 AM User is offline

the worst thing you can do is disable the POA system. Also, you do not have to disassemble the POA to make it a cycling clutch system. There are adaptors on the market that do this if that is the route you want to take. Just remeber, A6 compressors were never meant to be a cycling clutch system so a a different compressor will eventually be needed.

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