POA valve testing

[randy500]

Its real easy.
Picture shows flex handle and extension in outlet of valve for adjustment.
The nut is either 7 or 8mm or 11/32, its kind of an odd size.
Pressurize 100psi or so through evaporator with or without expansion valve in place. You will hear a soft pop then the valve should regulate to set pressure, approx 29.5psi for R12 and 27.5 psi for 134a.
Some valves have a honking sound when pressurized and regulating, thats fine but can sometimes be heard when running.
If the pressure is much higher or does not regulate then the POA valve is bad.

[davischevy]

Thanks for posting Randy.

[randy500]

Originally Posted by davischevy

Thanks for posting Randy.

Your welcome.
Its real neat testing them and adjusting them, then when its installed you known its going to work.
I just tested a couple last week, the pressure on the gauge rises above, then you hear the pop and it regulates down.

[Richard]

Thanks for this Randy. Will have to test mine and adjust. Kind of odd that the R-134A pressure is lower as it has a higher boiling point.

[randy500]

Temperature pressure chart for R12 and R134a
You dont want the evaporator under freezing, 32 degrees otherwise it will ice up from moisture in the ambient air which will stop airflow across it and cabin cooling. The chart shows the temperature at various pressures for each refrigerant. My quoted pressures are slightly below freezing for each refrigerant.

[Richard]

Agreed. Guess I just did not understand the POA valve's function in the system. Are there aftermarket R-410a TVX's? The R-12 TXV's are usually close enough to work okay. But since you have done a few I thought I would ask.

[randy500]

Originally Posted by Richard

Agreed. Guess I just did not understand the POA valve's function in the system. Are there aftermarket R-410a TVX's? The R-12 TXV's are usually close enough to work okay. But since you have done a few I thought I would ask.

I only know of using the stock expansion valve.

[CUSTOM/10]

Originally Posted by Richard

Agreed. Guess I just did not understand the POA valve's function in the system. Are there aftermarket R-410a TVX's? The R-12 TXV's are usually close enough to work okay. But since you have done a few I thought I would ask.

The POA valve is original GM, it is basically a back pressure regulator maintaining a certain pressure in the evaporator keeps it at a constant temperature.

[phlegm]

Hi guys, started on my AC system today, got all the parts etc.. I removed the High side/muffler hose and the Wet hose, hooked my gauges up to the low side valve and sent compressed air through the Evap coil and out the POA valve. I can hear a noise when I do this that sounds like the valve opening, but I am not seeing any back pressure at all. Everything I am reading says I should be seeing 20-30 PSI depending on how it is adjusted.

Can anyone confirm with this scenario that the POA valve is toast. It sure seems that way. I think I can get it rebuilt.

[randy500]

Originally Posted by phlegm

Hi guys, started on my AC system today, got all the parts etc.. I removed the High side/muffler hose and the Wet hose, hooked my gauges up to the low side valve and sent compressed air through the Evap coil and out the POA valve. I can hear a noise when I do this that sounds like the valve opening, but I am not seeing any back pressure at all. Everything I am reading says I should be seeing 20-30 PSI depending on how it is adjusted.

Can anyone confirm with this scenario that the POA valve is toast. It sure seems that way. I think I can get it rebuilt.

How much psi did you use? I use 125 or so.
By low side gauge hookup you do mean the port on the poa valve?
What psi was the gauge reading, even bad poa vslves i have tested regulated around 60 psi or so.

[phlegm]

Originally Posted by randy500

How much psi did you use? I use 125 or so.
By low side gauge hookup you do mean the port on the poa valve?
What psi was the gauge reading, even bad poa vslves i have tested regulated around 60 psi or so.

I took the hose off of the compressor side of the POA valve, then removed the liquid hose off of the expansion valve.

I put the Blue Gauge hose on the low pressure fitting on the POA. Then used a compressor to blow about 90 PSI through the expansion valve>Evaporator>POA valve. The gauge (which works, i tested it on my acura) did not show any pressure. So I take that to mean the POA Is stuck open and air is passing straight through, which is its normal failed condition from what I can research. It woudl make sense because my compressor locked up and most of what I can find says these things fail easily if any contaminants are in the system.

If it sounds like I am on the right track I am probably going to replace it with the OAP one that has the switch function on it and call it a day. Im not doing a Ground up OEM only resto, I just want decent air in NC to go a puttering down the road.

https://www.oldairproducts.com/produ...poa-update-kit

[davischevy]

If you put that OAP on there, prepare to be disappointed.

These systems work great when properly adjusted. I have one that was serviced 12 years ago and I drove it Saturday and it will freeze you out.

Look here. Randy described the procedure.
http://67-72chevytrucks.com/vboard/s...&highlight=POA

[phlegm]

Originally Posted by davischevy

If you put that OAP on there, prepare to be disappointed.

These systems work great when properly adjusted. I have one that was serviced 12 years ago and I drove it Saturday and it will freeze you out.

Look here. Randy described the procedure.
http://67-72chevytrucks.com/vboard/s...&highlight=POA

Right, he responded to me but probably went offline, he will be back I think. My issue is I think my POA is bad, so if I replace it I am thinking the OAP one.

[randy500]

You will not be happy with the OAP or whatever that crap is. The system is not designed to use that, it will work but its juste pure snake oil junk.
Try more pressure, the system always has more pressure than that.
I think i have an extra POA valve, i dont normally sell them Because i have a lot of trucks im building.
If i have one i will sell it for $135 shipped.

[phlegm]

Thanks Randy, I have found a place that will rebuild mine

[phlegm]

Ok guys, so I called Original Air group about rebuilding mine, cost is 234.00. He recommended that since I am replacing the Original A6 with the updated aluminum version that the updated ones actually work better with the POA that has the cycling switch on them. Just to verify I called 4 seasons and they confirmed the one i have is the updated type. So I am going to give this a go with the delete and see what happens. Also worth noting, he offered to trade me one of those cycle type POAs and pay me 45.00 for mine. So if you guys have any laying around you want to get rid of you can give them a call (original air group) and option out for restorations.

I will have to see how it all goes, just passing along the info I was given.

Thanks

[randy500]

That is the most foolish Thing i have ever heard.
A cycling system is he worst system made. Look at the temp pressure chart, assuming its cycling from 30 to 60 psi that would mesn the average temperature in the evaporator is about 45 degrees, is that what you want? Or do you want it constantly about 32 degrees for max cooling?
That cycling crap was a cost cutting measure by the auto manufacturers, its far inferior.

There are chevelle, corvette and camaro restoration forums, and autoac forum, nobody has ever been happy after installing the poa eliminator. Read up, nobody here has been happy either.
The clutch on the aluminum compressor is more robust and can take the constant cycling.
Can you accept reduced cooling and the constant racket of the clutch cycling along with the up and down engine load?

[randy500]

Are you downgrading to 134a too?
How crappy of a system do you really want here?
What people fail to acknowledge is that r12 and mineral oil is a virtual homogenous mixture so oil is always being moved through the system.
With 134 the oil can come out of suspension and rest in low spots, r12 and poa is far superior system for cooling and longevity.

[phlegm]

I have a seized POA valve, and a seized compressor... likely the result of a "certified" technician doing a death nail conversion on my original AC system to 134a. So converting back to R12 would include sourcing a POA or getting mine redone, going back a step in fittings (already have the replacement hose/muffler in hand) and picking up 3 or 4 cans of R12 which is pricey depending on where you source that. Along with fighting time... Son needs the truck and it aint getting cooler.

Doing what I can with what Ive got, thats all any of us can. Ill let you know how it goes.

[leddzepp]

Originally Posted by randy500

Are you downgrading to 134a too?
How crappy of a system do you really want here?
What people fail to acknowledge is that r12 and mineral oil is a virtual homogenous mixture so oil is always being moved through the system.
With 134 the oil can come out of suspension and rest in low spots, r12 and poa is far superior system for cooling and longevity.

I couldn’t agree more. I bought the upgraded aluminum compressor from autozone 3 years ago for my 68. It came as a kit, included compressor, expansion valve, drier/receiver, and a quart of mineral oil. Cost was $325 as I recall. I used r12 and the system has blown ice cold air and has worked flawlessly ever since. All factory original parts except for the upgraded aluminum compressor. No need for a different condenser, evaporator, or poa change.

[tdangle]

Originally Posted by leddzepp

I couldn’t agree more. I bought the upgraded aluminum compressor from autozone 3 years ago for my 68. It came as a kit, included compressor, expansion valve, drier/receiver, and a quart of mineral oil. Cost was $325 as I recall. I used r12 and the system has blown ice cold air and has worked flawlessly ever since. All factory original parts except for the upgraded aluminum compressor. No need for a different condenser, evaporator, or poa change.

Just looked, $408 today

[tdangle]

I'm considering switching back to R12. Mine works OK, but I think it would be cooler with R12. Just need to find a source for the freon. I've seen it on Ebay but when you look at the pictures cans are rusty and not really trusting it's full and good R12.

[mrein3]

Originally Posted by randy500

How much psi did you use? I use 125 or so.
By low side gauge hookup you do mean the port on the poa valve?
What psi was the gauge reading, even bad poa vslves i have tested regulated around 60 psi or so.

In every AC post I've made when talking about a POA valve I refer to that first picture. There was an awesome post on and AC forum that showed you how to adjust your POA and it was accompanied by that picture. I used to post the link to the instructions but they link was taken down and I didn't copy that photo.

You blow 60 psi in like the picture shows and like randy500 says you adjust your POA with your socket like the picture shows to 29.5psi for R12 (which should be the stock setting) and 27.5 (I thought it was 26.5) psi for 134a.

If you're re-habbing a stock AC system, copy this photo.

[Biscayne Stocker]

Thanks Randy500. Getting ready to put a factory AC setup in my girlfriend's 1970 C/20. This helps a bunch. Thanks for the info.

Scott

[phlegm]

I was able to get the AC / muffler hose off of that back fitting but my POA valve is stuck at the condenser side. So I have it soaking in PB Blaster now and plan to try a socket/crescent wrench combo to get that pulled. Just for records, the back side of that valve seems to be 1-1/4, I will keep this posted. If anyone has a better suggestion for getting it un stuck let me know. My next step if this doesn't work will likely be to remove the assembly from the box and work it on a bench somehow with a vice.