Model: C-10 Pickup
Engine Size: 350
Refrigerant Type: R12
I am having trouble locating a replacement POA for my 70 Chevy C-10 pickup. Can anyone
advise a source? Can the original be rebuilt?
The POA can't be rebuilt. But it CAN be tested/adjusted per listings in the archives. What makes you feel the POA is bad instead of the txv as suggested? And as pointed out, the oil bleed line is frosted. Might have crud in it. Also, the schrader valve core for the bleed line is a "special low pressure" core. NOT the same as other cores. Cool Pro #CPO190. Get them from Tim. For reference, your POA is a type 15-51. We know of 3 types, there may be more. Basically all the same, but the port configurations are different. For example, my car, a 1967 Impala SS uses the 15-52. But before ditching the POA, test it to be sure its is really bad. TXVs are a lot easier to find.
Thanks for the response Dave. I have already got the TXV and don't mind replacing the POA also while I'm at it. I don't want a chance at a do over. They market a POA retrofit kit which uses a thermal switch to perform the same functions. I researched the retrofit kit patent #5918476 and it shows and explains how the retrofit POA functions. I learned alot about the operating principles of the POA (Pressure Operable Valve) from the reading. The retrofit POA is sold by a company called
It you read some of my past posts, you will see that I am not a fan of the POA update kits. What type of compressor are you running? If its still the A6, that unit is not designed for clacking on and off. It was designed to run all the time for best cooling. This is just my opinion, but I think the best system ever designed was the A6/POA/txv. You said the kit you are looking at uses a thermo switch. Are you sure? Every one I've heard of used a LP switch that cycles the compressor.
I'm sure you researched the system, but all the POA does is hold the evaporator at 30 psig, regardless of load, for maximum cooling. Compressors that cycle on and off can't touch it.
I sure that you are correct about the POA being the better way to go. I there a simple test that could be conducted to verify that it is ok. Maybe an air pressure test to see if it actuates at the 30+ psi pressure point?
Thanks for the link Dougflas. That test set up is something that I invisioned when I ask the question.
Bob...I was able to find a NEW POA for my 67 buick from Cool Air in North Richland Hills TX.
Ask for the owner Wayne Herndon at 817 284 1888.
He had em in stock...havn't been able to find them anywhere else. Also he showed me a newer model
that functions like the original....not the retrofit recycling deal you mentioned.
Thanks for the contact gregg.
I did test the POA as described in the link from dougflas and what happen is as follows:
When starting to pressurize the inlet to the POA, air was coming out of the outlet. As the imput
flow was increased, the pressure rose on the low side gage until it stabilized at 30
psi. No matter how much the input flow was increased, the low side gage pressure would stay at 30 psi. There was no pop or definite turn on of the POA when the pressure reached 30 psi.
It sounds as though your POA isn't quite right. There should be no flow out of the POA until 30 psig inlet is reached. It should then modulate to hold 30 as the pressure increases. And on the down side, it should start to close ( trying to keep the evaporator at 30 psig) as pressure drops, and be closed at 30. Of course, these are R12 pressures.
When I made the decision to "deep-six" the POA "update kit" on my Impala, and go back to R12, I went junk yard shopping. I bought several POA valves. Think I paid $5 each. Kept the ones that tested good, trashed the rest. I would go that route rather than paying for a "new" one. Its probably $ 200-300, if it is really new, and will fit your vehicle. And stay far away from those "rebuilt" units on that auction site.
Thanks for the response Dave. I'll research my options to get a replacement POA.
Bob, I think your POA will work just fine. They all don't pop. As long as it regulates, it should work. You can try to shut the hand wheels, apply about 80 psi, and open the low side quickly. It may pop..may not. It seems to do its job and that is to keep the evap at 30psi
Bob and Doug
My reasoning behind why I think the POA my be malfunctioning is that Bob said it had outlet air flow as soon as he applied inlet air. The POA valves that I tested, and kept, did not have any outlet flow until after 30 psig inlet was reached. My thinking is this. If the tail coil temp is such that the txv starts to close, a leaking POA could allow the evap pressure to drop below 30 psig. Thus permitting the evap to start to freeze up. That is exactly what the POA is designed to prevent.
Anyway, just my $.02.
I have a new one for a Ford in stock. Will play with it this weekend if I can find the time. You have to realize that you're testing this off the vehicle with no TXV equalizer line connected nor an oil bleed line. Bench test is a little different than actual operating conditions. This test is jsut to see if it regulates the pressure and at what point.
Did you ever get the chance to test one of the POAs in your stock?
Damn, I forgot. Will do it today as I have an HVAC service call to make and I'll be in the garage after that. Will post back this evening.
POA will pop when I give it full 60lbs pressure and regulate at 30lbs. If I bring the pressure up slowly, no pop and it starts to regulate at 30lbs. If I increase supply to 60 from the 30 point, low side remains at 30. So depending upon test conditions, they may or not pop. The point that it does regulate at 30 is telling me it works.
When you bring the pressure up slowly from 0 to 30 psi, is there airflow through the POA. When I test mine,
there was airflow but POA maintained a 30 psi max pressure. When trying to increase pressure and airflow to 60 psi, the POA sounded like a foghorn.
when bringing it up slowly, yes there is airflow thru it. If you get the fog horn sound, I'd guess and think it was sticking. Give it a rap and see if the horn sound stops.
Just an update:
I was able to get a new POA from "Cool Air" located in Texas. A lead from gregg's post of 11/5/07. The price was $49.00. Before I install it, I will see how it tests out and post results.
Bob, You stole that POA!! $49.00 for a new one?? I just sold the last new one I had for $100.00; the guy was happier than a sprayed roach to get it.
I got a chance to test the POAs over the holidays. I retested the old one and it tested as was initially described to be acceptable -holding 30 psig ( got the foghorn sound but tapped it and the it start working as it should with a definite pop at 30 psig. When I tested the new one though, it didn't maintain any pressure up to 60 psig. I was very surprised - are there POAs with various pressure ratings?
Anyway, I decided to re-install the original POA with the new TXV valve, vacuumed down the system and recharged it with R12 by weight. I a/c is seems to be working fine now.
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