Adjusting stock POA for r134

[ApacheIvan]

I have all new AC in my 72. Everything is new except for evaporator and POA. New compressor, new hoses, new evaporator and expansion valve. When I bought the new hose with muffler on it I opted to go r134 so it has the proper valve in it already, converted the valve on the POA. With that said, I had it professionally charged. I was told since everything was stock that I should have had my POA pressure adjusted to get optimum cooling. Now that it all works, it blows cool but nor really cold. I hate that I have to evacuate the system again and take the POA out. Vintage Air is telling me I should get the kit that eliminates the POA and cycles the compressor. I don't like that idea, I would like it to look as stock as possible. Someone told me there was a guy on the forums that will service the POA for me but could not recall who it was. I did some searches but could not find him. If it is easy to do, I suppose I can do it myself, but don't have an air compressor at the moment.. so I am open to any and all suggestions.

[leddzepp]

Get rid of the 134 and go back to r-12. Your factory system will never function properly with r-134. I've gone through this many times....

[ApacheIvan]

Originally Posted by leddzepp

Get rid of the 134 and go back to r-12. Your factory system will never function properly with r-134. I've gone through this many times....

I have heard that too.. ugh.. expensive I will have to get a new muffler with the right fitting and pay a pretty penny for r12.. I may just do that..Learning from someone who has already spent the money

[ss454conv]

Going to R12 will be the best and freeze you out but I had a system in a Chevelle with 134 and an adjusted POA valve and it worked really well. I would say it was almost as good as my buddy's R12 system. For 134 to work well in an original system the POA needs to be adjusted, you need a A-10 compressor(A-6 will leak at the front seal) and a duel pass condenser.
I did not have the other two, only the POA and it was still good.
Good luck.

[Andy4639]

134-A will cool as good as any R-12 system ever would. If you do the system right and don't cut corners it will cool better. The POA valve may be the part that keeps the 134-A from cooling down and this is why they say replace it.
If it where me I would replace it and be done. If you keep it then go back to R-12.
134-A done right will cool as good are better than R-12! I have done my 71 C10, 64 SS Impala and the 56 Bel Air all in 134-A and it works great you just have to do it correctly.
As far as looking correct well most people (generally speaking) have no idea what they are looking at under a hood of a vehicle most of the time.

Lets see some tempatures of all these R-12 systems that are freezing cold guy's.

My C10:





The Impala:

[ApacheIvan]

Originally Posted by Andy4639

134-A will cool as good as any R-12 system ever would. If you do the system right and don't cut corners it will cool better. The POA valve may be the part that keeps the 134-A from cooling down and this is why they say replace it.
If it where me I would replace it and be done. If you keep it then go back to R-12.
134-A done right will cool as good are better than R-12! I have done my 71 C10, 64 SS Impala and the 56 Bel Air all in 134-A and it works great you just have to do it correctly.
As far as looking correct well most people (generally speaking) have no idea what they are looking at under a hood of a vehicle most of the time.

Lets see some tempatures of all these R-12 systems that are freezing cold guy's.

Ugh, I just spent 1000 dollars doing it right, but I guess I did it right for R12 because it is all stock. Everything under the hood is brand new. When you say most people don't know the difference, you mean anyone who doesn't know our trucks or Chevys for that matter. I guess I should't care if I want cold air

[davepl]

Originally Posted by leddzepp

Get rid of the 134 and go back to r-12. Your factory system will never function properly with r-134. I've gone through this many times....

You have, at which point I normally chime in to say that (with a parallel flow condenser) my factory system works AWESOME with R-134.

It's entirely possible the PO made changes or adjustments to the POA valve, as it already had the 134 fittings when I got the truck. But it's stock pieces so far as I can tell, except the condenser as noted. Oh and I suppose I should admit that I changed the compressor later, but that was for a leak. So I'll go with "stock appearing" R-134 and you can be "actually stock" R-12.

So I reject your theory! R-134 is the solution to every problem! With suitable disclaimers attached!

That said, if I had a functioning R-12 system that I was sure wasn't going to leak that pricey stuff back out, I'd just stick with R-12 myself. But if I wasn't sure, I'd rather leak R-134 than R-12.

[engineer_gregh]

You need to talk with F.A.A Benny. He is on the forum and can adjust your POA valve. As leddzepp said R12 is best but 134a will work with a lot of changes. A parallel flow condenser or at least one to two pusher fans on a standard condenser is required. I just rebuilt mine and have a pretty detailed thread on the subject. Andy above is also correct but notice all the changes he has made; he has installed a modern compressor, replaced his POA and expansion valve with an accumulator, pressure switch, and orifice tube and is running a parallel flow condenser.

[leddzepp]

Originally Posted by engineer_gregh

Andy above is also correct but notice all the changes he has made; he has installed a modern compressor, replaced his POA and expansion valve with an accumulator, pressure switch, and orifice tube and is running a parallel flow condenser.

Exactly!

Every time I post about r-12 being superior to r-134 in a FACTORY system he goes on about how it isn't...yet his system isn't factory anymore...which is my point! I have no doubt it works; it better after spending $1200 on the changes.

[Andy4639]

It is factory looking!

It was 134-A with all internals for a 71 when I did it the first time. It did fine but I knew it could do better and that's when I swapped everything out.
Back when I did the AC the first time though nobody was doing the POA valves so it would cool but not like it does now. When I did do the swap it was easier to just swap it out for the newer stuff.

ApacheIvan
When you say most people don't know the difference, you mean anyone who doesn't know our trucks or Chevys for that matter. I guess I should't care if I want cold air

Yes that was what I meant by the general public.
Unless you are going for 100 point show vehicle why worry what is factory are not, If you drive it like I do then comfort is what I go for.

Here are a couple of pictures of the SS for you also. By the way the SS has the A-6 compressor in it. It runs fine so far but it just got charged up this past winter so time will tell.

[Andy4639]

Originally Posted by leddzepp

Exactly!

Every time I post about r-12 being superior to r-134 in a FACTORY system he goes on about how it isn't...yet his system isn't factory anymore...which is my point! I have no doubt it works; it better after spending $1200 on the changes.

I have less than that in the whole system with the swap. But ok you got me on this. It isn't factory internally but what most people see is a factory unit. Because most don't know.

[engineer_gregh]

F.A.A Benny is in TX, not sure which city. You can private message him and I'm sure he will respond. He restores AC systems for a lot of different vehicles. His work is top notch! Now that I went through your build thread, I completely understand why you want to keep it original. Keep it R12, just my .02 cents.

[ApacheIvan]

Originally Posted by engineer_gregh

F.A.A Benny is in TX, not sure which city. You can private message him and I'm sure he will respond. He restores AC systems for a lot of different vehicles. His work is top notch! Now that I went through your build thread, I completely understand why you want to keep it original. Keep it R12, just my .02 cents.

Thanks for the heads up, that is exactly what I am doing, He does not live far from me either and if he can do the evacuation and recharge the better. I will just take him the truck. And yeah, it has huge sentimental value and needs to be just like it was when dad bought it. He has been off this earth now 20 years this year and I vowed to restore it to it's full glory. Interestingly enough his other baby which I am looking for is a 1964 Chevy Impala SS that was his first new car and one that was stolen out of his driveway in the mid 80s. That is the only thing on my bucketlist that I have not found yet

Thanks again for taking the time and pointing me in the right direction.

[Low Elco]

PM ls1nova71 on here. He has 2 of these trucks that look dead stock and blow icebergs. I believe he uses the biggest parallel flow condenser he can get and switches to a squarebody unit in the cab box. IDK, i just know it works and how!

[Andy4639]

My 64 SS Impala blows at 36* with a stock system. When I bought it the guy had done the 134-A swap but it wasn't working. I redid the lines and got it back in shape. It has been fine all summer so far.
I added the longer lines to hide them inside the fender and a new dryer. Vacuumed and charged it.
As I have stated before if done right doesn't matter which Freon you use. Getting 40 year old fittings to seal off is the hardest part to do.

[notsolo]

As long as were beating this to death! Whats the going rate for R12?....If you know somebody you might get a deal, 15 yrs ago local shop here was charging $400.00.to evacuate and charge.....I changed and charged my 93 over to 134a for $165.00 no regrets....I'm not the purest, I like the modern engine and 1 belt....If you like keeping it total stock, Excellent, its your boat.

[Big Block]

Ok guy's this is all new to me. Just bought a 71 Chevy Custom Deluxe Short Bed with factor air. It appears to be intact and complete. The previous owner did a new heater core. It has the original compressor on it but the system is empty and the compressor won't engage. I have a factory style replacement compressor. Should I replace the receiver, dryer, and compressor and pull a vacuum to see if it holds. If it does hold a charge, would you go ahead and charge it with r12. Or just replace everything first and upgrade everything to 134. The system hasn't worked for over 20 years.

[F.A.A.benny]

Originally Posted by Big Block

Ok guy's this is all new to me. Just bought a 71 Chevy Custom Deluxe Short Bed with factor air. It appears to be intact and complete. The previous owner did a new heater core. It has the original compressor on it but the system is empty and the compressor won't engage. I have a factory style replacement compressor. Should I replace the receiver, dryer, and compressor and pull a vacuum to see if it holds. If it does hold a charge, would you go ahead and charge it with r12. Or just replace everything first and upgrade everything to 134. The system hasn't worked for over 20 years.

I'd be worried about there being an issue with the poa valve. If its stuck, you wouldn't know it just by holding a vacuum

[leddzepp]

I can buy r12 on craigslist for LESS than r134 at autozone here, so the cost savings is a myth.

I really don't care what anyone does with their ac system, I post what works and I have cold air in ANY condition.

If people want to run around the block 6 times chasing cold air, throwing money at what might work or work marginally, that's fine. I'll just hit the easy button and walk next door.

[ApacheIvan]

I am going to leave it to Benny I have a PM to him waiting a reply.. I live within 30 miles of him, and instead of figuring it out myself, paying for multiple charges and taking things apart and "trying" out a bunch of stuff, I will leave it to the expert When I am done it will look stock, if he recommends r12 I will hit eBay, (surprised it is not a restricted buy) if he can get it cold with r134 for this Texas heat, then I will post my report after we are done if he will help me

[tdangle]

Originally Posted by leddzepp

I can buy r12 on craigslist for LESS than r134 at autozone here, so the cost savings is a myth.

I really don't care what anyone does with their ac system, I post what works and I have cold air in ANY condition.

If people want to run around the block 6 times chasing cold air, throwing money at what might work or work marginally, that's fine. I'll just hit the easy button and walk next door.

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.

[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

[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.

[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.