Model: delta custom
Engine Size: 455
Refrigerant Type: 134a
Ambient Temp: 85
Pressure Low: 40
Pressure High: 260
Country of Origin: United States
Hello everyone. new here. I have a strange problem with my system, and wondered if anyone else has seen this or knows what is wrong. The system has been flushed, new compressor a6, dryer, o-rings . pulls a great vacuum, and will hold it for a day or two. charged it with 134a, various amounts, will cool, but not get cold. Poa valve self adjusted with 60 -70 psi blowing in it to a setting of 26 psi on my gauges. run the a/c and you get the pressures around 40 on the low side, and better than 250 on the high side. put less charge, reading the same. weird thing is when you turn the a/c off the gauges hold their readings for around 10 minutes before they equalize. I first thought a bad expansion valve, but not sure. the fact of the pressure not dropping quicker than it does when you turn it off has me baffled? Thanks Terry
About 15 years ago, I had a 1969 Olds Cutlass. I also tried to do the retrofit. Of course, this was before I really knew what I was doing. Had never worked with a POA valve before. I sometimes wish I could have that car back to try again. I could get it cool, but not cold. I think the pressures holding after the compressor is turned off is a good thing. That tells me the check valves in the compressor and the POA are sealing well. If I recall, I fought very high high side pressure, like around 350 psi. I also had no idea to adjust the POA. It would hold the low side too high even at night with no sun load. Best I could get was 55 degrees or so. You have adjusted the POA. It should cool. My guess is that you have the original condenser, and it is not good enough for R134a. Also, what about the fan clutch? Is it new? Needs to be. Do you have the right fan shroud? Anyway, spray some water on the condenser and see what the temps and pressure do. I'd be if you wet the condenser, it will get into the 40s. Also, that car should have a vacuum heater valve on the intake manifold (mine did) Make sure it is shutting off when the AC is on.
thanks for the reply, yes it is the old condenser, new clutch and the heater valve is new and working properly. I still don't understand why the low side is so high after adjusting it. It reads higher than it would with the r12 in it. I found a jug of r12 after I had already adjusted the valve and had the hoses made, so I decided to stick with the 134a. As much trouble as I am having, I'm still gad I did. With the recovery system, I'm not really losing much freon, but I would hate for it to be r12 and lose any!
My understanding is that the POA valve prevents evaporator freeze up by maintaining a minimum pressure in the evaporator. The POA only functions if the evaporator gets too cold. When the car is hot, the suction pressure, along with the discharge pressure, will rise. Get the high side down and the suction pressure will go down too, as well as the vent temps. You might need a new, more efficient, condenser. What are you getting for vent temps at 40 psi suction? Does the pressures get any better as the interior cools off?
vent temps 58-60 sitting in my shop at night with a good fan blowing on the condenser! a/c also in the recirculate mode....... it only has that and normal mode. Pressures do not change. Pressures are the same even with only 2lbs of charge
I had a similar problem I almost never figured out with my 71 Delta Custom. I discovered Olds offered four different temp settings on their fan clutches that year. Once I found one with the correct setting, I replaced the so called "universal" unit and problem solved. Consult the factory service manual for more information.
Unplug the blower motor. Set the rpms to 1500. What are the pressures and temps? Make sure you have a window fan blowing into the condenser area.
will give this a try tonight if I get the chance. I run a squirrel cage fan in front of the car.
did this a few years back and had similar problems. added an aftermarket pusher fan in front of the condensor and solved most of the problem. an r-134 condenser is sized differently than an r-12, so the amount of heat removed is greater with a 134 part. head pressure dropped 25 pounds with an extra fan.
by the way, old poa valve were famous for the points sticking. often this can be corrected by TAPPING and not beating on the valve. watch your pressures when you do this.
finally, the advise given to make sure your heater valve is completely closed is very wise. i also recommend you check this as well.
Been a long time since I worked on a POA system, sometime in the early 70's and of course, strictly R-12. Pressures are kind of worthless as the compressor was running all the time, GM even came out with a charging system to charge by weight. But could work around that by adding charge until the evaporator outlet temperature approached the inlet temperature.
Also could feel pulsations in the high side line that would disappear, but this had to be done at around 85*F. POA is essentially a pressure regulator that outputted 28.5 psi to a TXV that was another goal, to hold the pressure over the temperature range. A6 did have a sump in it to assure lubrication with low refrigerant flow. These systems were great when even driving in a 125*F ambient, that I do remember.
Fan clutch was kind of an option back then, still a piece of trash, but at any wrecking yard could find a standard fixed fan that fitted and worked properly. And any wrecking yard was full of these as those bodies rusted out so quick.
An old member, Mitch, was going to dig into these systems, but unfortunately died several years ago. As many were having problems converting to R-134a. Still have one R-12 vehicle left and enough R-12 for a couple of more charges. But wish I was half awake in 1994 when they were giving this stuff away. Now R-134a is going to be a problem, just getting tired of fighting this.
Thanks to all for their help and suggestions, I recovered the system again.....and adjusted the poa valve on the car this time. Mine is the old style that you adjust on the outlet side. I have cold air and much lower temps. Still have not road tested. It was raining tonight and that car has too much realestate to have to clean if you don't have to. I had a low side at 27-28 and a high side around 205 -210 wasn't really hot in the shop till I got the big block running, forgot to measure the temp, but I was sweating around the car so I figure it was plenty warm in front of it also. Kept the fan in front, like last time. I guess my initial adjustment of the poa valve was wrong. I really wanted to test it again with the same pressure to see what the gauge said, but i was tired of fighting it and this way I only removed one hose. Somehow I think the setting of 25# with only 60+# blowing into it was not low enough. I backed it out at least another 1/4 to half turn. Anyway it works! also charged with 3lbs. Original was 3.75 r12
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