Adjusting stock POA for r134

[Andy4639]

I got a newsletter today from Orignal AIR group


About POA Valves


Pilot Operated Absolute (POA) Valves are the Suction Valves that were used on most mid 60's to mid 70's GM vehicle air conditioning systems and on some 70's Ford systems.

Frequently Asked Questions





What does a POA Valve do?

All air conditioning systems have something built into the system to prevent the
Evaporator from getting so cold that it freezes. In some systems, this mechanism is a thermostat, but in most mid 60's to mid 70's GM vehicles and some 70's Ford vehicles, it's a POA (Pilot Operated Absolute) Valve.

A thermostat prevents the Evaporator from freezing by cycling the Compressor on and off based on Evaporator temperature. A POA Valve prevents the Evaporator from freezing by by-passing excessive system pressure. Note that in a POA Valve type system, the Compressor runs constantly whenever the air conditioning system is operating.

As long as the Evaporator pressure remains above a predetermined level, the POA Valve remains open, allowing Refrigerant to flow freely out of the Evaporator. When Evaporator pressure drops below that level, the POA Valve closes and the Refrigerant flow out of the Evaporator is restricted. The pressure in the Evaporator then increases, which increases the temperature in the Evaporator and prevents the Evaporator from freezing.

Most POA Valves also regulate Evaporator pressure through a pressure equalization line connection back to the Expansion Valve that balances the pressure of the Refrigerant entering the Expansion Valve and thereby regulates the amount of Refrigerant the Expansion Valve allows into the Evaporator.

The POA Valve also aids circulation of oil to the Compressor through an oil bleed line connection to the bottom of the Evaporator through which oil that collects at the bottom of the Evaporator is forced by Evaporator pressure back into the Refrigerant loop.

Fun Fact

A POA Valve operates independently of atmospheric pressure and is not affected by changes in altitude.



How does a POA Valve fit into the air conditioning system?

The POA Valve mounts directly to the Evaporator's suction outlet, with normal flow of Refrigerant right through the valve's female end fitting and out the male end fitting. Some Ford POA Valves have two or four additional fittings but most of them and all the GM POA Valves have three additional fittings:

(1) A male charge fitting (for connection to an external manifold gauge);
(2) a male oil bleed line fitting (which connects to the long skinny line from the Evaporator Coil); and
(3) A female pressure equalization fitting (which connects to the male nut on the Expansion Valve capillary tube).



Are there different types of POA Valves?

Depending on the model, General Motors cars & trucks used one of three different POA valves, all of which were made in Frigidaire, then Delco versions. Depending on the model, Ford used one of nine different POA valves, all of which were made only in Delco versions. Delco valves cannot be rebuilt, but we may be able to recondition yours or offer an NOS replacement.

POA Valve Types






Any POA Valve issues when restoring car?

If your air conditioning system has not been operating for a while, it is probably best to test your POA Valve as part of the restoration of your vehicle.

Also, if you are converting to 134a Refrigerant, your POA Valve will need to be recalibrated to by-pass at a different rate than it did with the old R12 Refrigerant.

You can send your POA Valve to us and we can test it for you. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and it fails any of the tests, we can completely rebuild it. See the "What is POA Valve Reconditioning?" and "What is POA Valve Rebuilding?" questions below.



Is my POA Valve failing?

To find out, most customers choose to send us their POA Valve and let us test it. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and it fails any of the tests, we can completely rebuild it. See the "What is POA Valve Reconditioning?" and "What is POA Valve Rebuilding?" questions below.

Alternatively, you or your mechanic may be able to determine if your POA Valve is failing during system evaluation using gauge manifolds. A POA Valve will generally fail in the open position, letting high pressure vapor into what should be the low pressure side of the A/C system. If the POA Valve is failing, you'll have little or no cold air coming out the vents when the air condition system is operating and the high side reading will be normal but the low side reading will be high. (Because the failing POA Valve is letting high pressure vapor into the low side of the system).

A properly functioning POA valve equipped system with R12 refrigerant will have a low side readings on POA valve of right around 30psi, while systems using 134a refrigerant should read right around 20psi, once calibrated.

High side readings can vary depending upon the refrigerant, outside temperature and humidity but should generally fall within the following ranges:

134a
High Side Readings (Fahrenheit) Outside Air (Ambient) Temperature
115-200 70-80
140-235 80-90
165-270 90-100
210-310 100-110



R12
High Side Readings (Fahrenheit) Outside Air (Ambient) Temperature
130-160 60
140-170 65
150-180 70
160-190 75
170-210 80
180-220 85
190-230 90
205-250 95
220-270 100
240-290 105
260-310 110
285-335 115
310-370 120

graphic



Suggestions for a failing POA Valve?

If your POA Valve is failing, first determine if it is an original Frigidaire. See "Are there different types of POA Valves?" above. If it is, send it to us and we can either rebuild it and return it to you or send you a rebuilt replacement. See "What is POA Valve Rebuilding?" below.

If it is not an original Frigidaire, it cannot be rebuilt and you'll need to order a replacement from us.



Any POA Valve issues when converting to 134a?

If you are converting to 134a Refrigerant, your POA Valve will need to be recalibrated to by-pass at a different rate than it did with the old R12 Refrigerant.

You can send your POA Valve to us and we can test it for you. If it passes a series of tests, we can recondition and recalibrate it for you. If it is a Frigidaire Valve and it fails any of the tests, we can completely rebuild it. See the "What is POA Valve Reconditioning?" and "What is POA Valve Rebuilding?" questions below.



What is POA Valve Reconditioning?

POA Valve Reconditioning is the restoration service we perform on a POA Valve that passes our initial tests. We can perform these services without having to cut the POA Valve open. POA Valve Reconditioning includes:

- Initial tests
- Flush clean
- Lubricate
- Calibrate for R12 or 134a
- Zinc plate
- Final tests

> Ford POA Valve Reconditioning
> GM POA Valve Reconditioning



What is POA Valve Rebuilding?

POA Valve Rebuilding is the restoration service we perform on a Frigidaire POA Valve that fails any of our initial tests. To perform these services, we must cut the POA Valve open in order to repair it. (We then weld it back together, pressure test and zinc plate it once repairs are finished).

Rebuilding is only available on original Frigidaire Valves. It is not available for Ford Valves or Delco replacement valves. To understand the difference, see "Are there different typed of POA Valves?" above.

POA Valve Rebuilding includes:
- Initial tests
- Cut open
- Disassemble
- Inspect
- Clean and repair or replace damaged parts
- Replace seals
- Reassemble and weld back together
- Lubricate
- Test and calibrate for R12 or 134a
- Zinc plate
- Final tests

> GM POA Valve Rebuilding



What's a Core Charge?

Since many rebuilt & reconditioned parts are no longer made, our ability to provide them on an outright basis depends on our ability to maintain inventory known as cores. The sale of a rebuilt or reconditioned part often carries a "core charge," which is a form of deposit that is paid until your original part can be returned, or as a means of purchasing a part without returning anything if you don't have the core to return to us.

For example, let's say you want to buy a rebuilt POA valve, but you haven't removed the old valve from the car yet. You pay an additional core charge up front when you buy the valve. Once the old valve is removed from your car and replaced, you return the old valve with your receipt (which includes the core charge), and as long as the old part is in acceptable condition, the core charge is refunded.

> 15-51 Type 1 POA Valve
> 15-51 Type 2 POA Valve
> 15-52 POA Valve

[F.A.A.benny]

I used to work for them l, Andy. On my first day there that's where they put. Rebuilding poa valves

[rsgt]

Here is mine. It is 93 out today. Sitting out in the yard idling I got 42 in the center vent. When I bought my truck the compressor was in the bed of the truck. I flushed the lines, replaced the dryer and expansion valve, bought an aluminum replacement compressor. I bought R12 at a swap meet for $20.00 a can.

[engineer_gregh]

I bought 12oz. cans of 134a on clearance at Big Lots for $2.00 each, I live right outside Nashville TN; Yea I bought two cases at that price. Normal prices here average $5 a can if you shop around. The biggest rip off is the larger cans with the hose and gauge for $39.95, you're pretty much guaranteed to screw up you A/C system with it and you pay more for the privilege. R12 will cost you $30-$50 a can, if you can find it. And yes there are EPA restrictions selling or purchasing R12.

[engineer_gregh]

Another note; the oil used for R12 and R134a are not compatible! There are hack shops out there that will evacuate an R12 system and charge with R134a. That will absolutely fail, period, no question. With just evacuating a system you still have oil left in the compressor. Senior members on this board have suffered the bumps and bruises, and paid the cost to learn these things. Guys like leddzepp, Andy, Dave, and numerous others are nice enough to share their experiences, much appreciated guys. And just in case you hadn't noticed they can get pretty passionate about their trucks! Just do your homework and ask questions on this board and you will get the answers you need to get your truck in the desired condition you seek.

[Andy4639]

Originally Posted by engineer_gregh

Another note; the oil used for R12 and R134a are not compatible! There are hack shops out there that will evacuate an R12 system and charge with R134a. That will absolutely fail, period, no question. With just evacuating a system you still have oil left in the compressor. Senior members on this board have suffered the bumps and bruises, and paid the cost to learn these things. Guys like leddzepp, Andy, Dave, and numerous others are nice enough to share their experiences, much appreciated guys. And just in case you hadn't noticed they can get pretty passionate about their trucks! Just do your homework and ask questions on this board and you will get the answers you need to get your truck in the desired condition you seek.

Thanks,
I try and help people all I can. We all learn from each other.
Another note that a lot of people may are may not know. A good AC shop guy will want to know if your system is R-12 are 134-A before they do anything to it. The recovery machines can only do one are the other. They can't mix the 2 together. I have had some even tell me they don't want the synthetic stuff either in their machines like you buy at the parts stores. 134-A freeze and AC Pro.
I took both my 71 and Impala to my guy who charges me $50.00 to vacuum and charge the system. He only uses 134-A no synthetic stuff. I had to take the truck stuff a part this past spring and flush out the system because the 20 year old accumulator desiccant had failed and clogged up my orifice tube.
The Impala was a first time job.

[ApacheIvan]

Originally Posted by engineer_gregh

Another note; the oil used for R12 and R134a are not compatible! There are hack shops out there that will evacuate an R12 system and charge with R134a. That will absolutely fail, period, no question. With just evacuating a system you still have oil left in the compressor. Senior members on this board have suffered the bumps and bruises, and paid the cost to learn these things. Guys like leddzepp, Andy, Dave, and numerous others are nice enough to share their experiences, much appreciated guys. And just in case you hadn't noticed they can get pretty passionate about their trucks! Just do your homework and ask questions on this board and you will get the answers you need to get your truck in the desired condition you seek.

I think I am just going to buy the right R12 hose for the compressor, evacuate and flush the r134 out and put R12 back in it. I spent too much money for all the OEM stock components to switch it all out, I could adjust the POA and "hope" it works with the possibility of not being happy..and just have to do it again. I only have one component in the system that cost about 100 bucks to replace to make it so. Not looking forward to the cost of the R12 or taking it all back apart to get all the old oil out of it, but if I want cold air I guess I have to Everything I read says 3.25 lbs (right around 52oz if my math is correct) and 8oz of oil. Fun!

[leddzepp]

I think the thing EVERYONE who has done AC work can agree on is that you do NOT use synthetics, additives, or "stop leak". That stuff is proprietary crap that will ruin a system. R-12 or R-134 only, nothing fancy. No AC shop will touch a system that has anything other than freon used. When I see someone in line at the store with some of those "fancy" freon cans I just shake my head.

[Bigdav160]

Isn't PAG synthetic oil? It is the only oil recommended by the OE. They warn about using esters.

[mrein3]

I converted a non-AC cab to AC with factory parts. I did a write up about it here:
http://67-72chevytrucks.com/vboard/s...d.php?t=478564

The adjust POA link no longer works. Sorry about that. I did adjust mine and it works good. You can always adjust it back and run R12.

[71CHEVYSHORTBED402]

Originally Posted by tdangle

Now that I've fixed the leaks in my system, I would love to switch back to R12. As Leddzepp says without a bunch of work and mods, imo, R134 doesn't work as well. Cool but not super cold like my DD (15 Challenger Hemi RT). Best I can find on CL is about $35 a 12 oz can. Although not cheaper than Autozone R134 where I just bought at 2 12oz cans for $20. I'll just keep on looking.

Zep. has an interesting perspective, so I looked. At the moment Reno Craigslist has 12 Oz cans for $22 each or OBO, and there's a 30 pound bottle for $400ish.

Just for (*&()^, from my education to-date, this identifies the system and what's required for 134a conversion. Corrections welcome:

Original Evaporator: Works for R12 & R134a

Original Expansion valve: Works for R12 & R134a

Original POA valve: Works for R12 & R134a, though must be calibrated for what you're using.

Original Muffler: Does not work for R134a.

Original hoses: Word is the original hoses do not work for R134a. Un-confirmed.

Original compressor: Works for R12 & R134a

Original O-rings: Do not work for R134a.

Original Dryer: Does not work for R134a.

Original Condenser: Works for R134a, but not as well as serpentine replacements, which remove heat better. The original condensers are tubed.

[F.A.A.benny]

You can put an adaptor fitting on the muffler manifold. I'd replace the hoses but there are those that do not. I'd really consider changing them if the fittings were clamped instead of crimped

[davepl]

Originally Posted by 71CHEVYSHORTBED402

Zep. has an interesting perspective, so I looked. At the moment Reno Craigslist has 12 Oz cans for $22 each or OBO, and there's a 30 pound bottle for $400ish.

Just for (*&()^, from my education to-date, this identifies the system and what's required for 134a conversion. Corrections welcome:

Original Evaporator: Works for R12 & R134a

Original Expansion valve: Works for R12 & R134a

Original POA valve: Works for R12 & R134a, though must be calibrated for what you're using.

Original Muffler: Does not work for R134a.

Original hoses: Word is the original hoses do not work for R134a. Un-confirmed.

Original compressor: Works for R12 & R134a

Original O-rings: Do not work for R134a.

Original Dryer: Does not work for R134a.

Original Condenser: Works for R134a, but not as well as serpentine replacements, which remove heat better. The original condensers are tubed.

Weird that mine works with all original parts except the condenser, and even then I went parallel and not serpentine, so I guess that's "wrong" too.

My system blows 40F with R-134 and factory parts.

I think the notion that all of the factory parts are incompatible with R-134 flies in the face of the fact that mine works great.

Now granted I used all new "old" parts, so I don't have a bunch of the old oil, and I used green and grey o-rings. So it's never as simple as just filling the old system with R-134, of course. I also wound up with a new compressor because of leak at the snout, which is apparently common. Basically, if LMC Truck sells it, I installed a new one of it. But they're all reproductions of original parts, not "special" R-134 parts, so far as I can tell.

This thread in particular has a lot of doom and gloom and pounding the table about how what many of us are doing successfully absolutely cannot work.

I'm not telling anyone what to do. Just saying mine works great.

[ApacheIvan]

I bought the muffler that already has the R134 fitting on it. Had to put the r134 adapter on the POA. If I knew that all I had to do was adjust the POA I would give that a shot. BUT I bought the stock style condenser, which Benny said I would need to replace to run 134.

[leddzepp]

Originally Posted by davepl

Weird that mine works with all original parts except the condenser, and even then I went parallel and not serpentine, so I guess that's "wrong" too.

My system blows 40F with R-134 and factory parts.

I think the notion that all of the factory parts are incompatible with R-134 flies in the face of the fact that mine works great.

Now granted I used all new "old" parts, so I don't have a bunch of the old oil, and I used green and grey o-rings. So it's never as simple as just filling the old system with R-134, of course. I also wound up with a new compressor because of leak at the snout, which is apparently common. Basically, if LMC Truck sells it, I installed a new one of it. But they're all reproductions of original parts, not "special" R-134 parts, so far as I can tell.

This thread in particular has a lot of doom and gloom and pounding the table about how what many of us are doing successfully absolutely cannot work.

I'm not telling anyone what to do. Just saying mine works great.

You don't live in the desert where temps hit triple digits. It might be a different story then.

[Andy4639]

I think this is a great thread. It has helped a few guy's out and it has shown what some of us have done and find new ways of doing things.

I haven't even mentioned my $5.00 micro switch mod that cuts the fans off at highway speed when the AC is on.

Before anyone says you can have the ECU turn them on and off your right as long as the AC isn't on. My mod works either way and it has been working now for over 2 years and I did the same mod on the 64 SS Impala to.
I hope it helps the life of my fans by doing this.
My truck isn't factory correct and I never wanted to be. I like driving mine to much to leave it factory. My truck was manual everything when I bought it.
I added the AC my self back in the 80's. I did away with the cowl vent and I keep the heater core hoses closed during the summer months and sealed up the radiator area to force the air through it not around it plus the radiator fill panels. My truck cools at 38* all day long and as long as the truck is moving the fans never come on even when the AC is off.

[71CHEVYSHORTBED402]

Originally Posted by leddzepp

You don't live in the desert where temps hit triple digits. It might be a different story then.

Still interesting to learn. Nothing like first hand experience. How long has it been installed, Dave?

Interesting read Andy4639. I recently learned how to assemble an original system, and that information provided the why.

[engineer_gregh]

My comments (in italics) on Tony's earlier post are based on my own experience in rebuilding the A/C on my 71 money pit. It blows 42 degrees with R134a.

Just for (*&()^, from my education to-date, this identifies the system and what's required for 134a conversion. Corrections welcome:

Original Evaporator: Works for R12 & R134a

Original Expansion valve: Works for R12 & R134a

Original POA valve: Works for R12 & R134a, though must be calibrated for what you're using.

Original Muffler: Does not work for R134a. Not true, it can be used with an adapter. R12 and R134a use different fittings for servicing.

Original hoses: Word is the original hoses do not work for R134a. Un-confirmed. Not true, but if your hoses are terminated with clamps versus crimped you should change them. If they are original and 40+ years old I would change them.

Original compressor: Works for R12 & R134a

Original O-rings: Do not work for R134a. Not true

Original Dryer: Does not work for R134a. Not true, but a new one at Auto Zone is $12.99 so change it.

Original Condenser: Works for R134a, but not as well as serpentine replacements, which remove heat better. The original condensers are tubed. I believe you meant parallel flow not serpentine. 100% correct although if you add pusher fans to the tubed typed condenser it helps in dissipating the heat.
__________________

[Rufas]

Originally Posted by rsgt

Here is mine. It is 93 out today. Sitting out in the yard idling I got 42 in the center vent. When I bought my truck the compressor was in the bed of the truck. I flushed the lines, replaced the dryer and expansion valve, bought an aluminum replacement compressor. I bought R12 at a swap meet for $20.00 a can.

I know this is totally off topic.

I saw a recent FamtomWorks on Velocity. They charged a customer $1,500 per can of R12!!!!

Oh well back to the main topic.

[anew4961]

I put r12 back in mine and it cools down to 38 degrees at idle what's better than that

[ApacheIvan]

Originally Posted by anew4961

I put r12 back in mine and it cools down to 38 degrees at idle what's better than that

Did you do it yourself? What all did you have to do to accomplish that and what was the final cost?

[anew4961]

Originally Posted by ApacheIvan

Did you do it yourself? What all did you have to do to accomplish that and what was the final cost?

everything is original except compressor ,lines and updated poa valve I flushed and cleaned the system with brake clean then flushed with water then blowed it dry with compressed air drained new compressor of oil put new oil in compressor filled with R12 I worked on transport referigation with compressor and other parts around 4 o 5 hundred dollars I was smart years ago and kept 3 30 lb. tanks of r12

[ApacheIvan]

Originally Posted by anew4961

everything is original except compressor ,lines and updated poa valve I flushed and cleaned the system with brake clean then flushed with water then blowed it dry with compressed air drained new compressor of oil put new oil in compressor filled with R12 I worked on transport referigation with compressor and other parts around 4 o 5 hundred dollars I was smart years ago and kept 3 30 lb. tanks of r12

What is updated on your POA?

[davischevy]

I have to smile when I read this thread. I bought a 1972 Cheyenne new, and almost from day one there have been arguments about whether the AC worked well on them.

[F.A.A.benny]

Originally Posted by ApacheIvan

What is updated on your POA?

He is refering to a poa delete kit which is essentially just a tube with a cycling switch on it. If your poa valve is good you should stick with that.