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Okay where do I start... I have bought all new/rebuilt AC equipment during these last three to four years from different vendors (parallel flow condenser, drier, AC box w/blower, expansion valve & POA valve (adjusted for R134), all new hoses, and had the compressor rebuilt. I had completely taken apart the car and went through all the AC vacuum hoses and checked to make sure everything operated correctly. I placed 10.5 ounces of Ester R134a refrigerant oil in the compressor after draining out the oil that the vendor had placed in the compressor for shipping purposes. I then turned the compressor by hand ten revolutions and then placed it into the car. Again, everything is new or rebuilt in this system.
I went to a local repair shop that does AC and they put 3.2 lbs of R134 into the car. When the mechanic tried the AC, the compressor was engaging, he was getting air out of the vents but it was not cold nor cool. As the mechanic was checking the system he noted to me that the beginning and towards the middle of the POA valve was very cold but the other side of it where is goes off into the evaporator was warm - not cool. The mechanic did not know much about this system and thought there was a bottleneck happening there in the valve. He said to take the car home and see if I could figure out where the issue was and then bring it back to him to evacuate the system again if I need to change a part out - the mechanic stated he would not charge me for the services to evacuate the system since I had already paid for the freon and he would put it back in once I corrected the situation.
I took the car home and checked to see if I had everything tightened and that all seemed good. I then placed a set of gauges on it, the low side read 90psi and the high side read 150 psi. I thought maybe there might be too much freon in the system and I went back to the shop where he evacuated all the refrigerant out of the system and then placed 2.5 lbs of refrigerant back in. We again tried the AC but still no cold air, the POA valve was doing the same thing again - very cold on one side and warm on the other. I had him evacuate the R134 out of the system again and I brought the car home. When I got it home I searched on the web on how to test a poa valve. I followed what the youtube video
showed and I took off the lines on the poa valve and the expansion valve and hooked up my low side pressure gauge to the POA's low side valve and the took my compressor and blew air through the expansion valve and it showed I had pressure of 27 psi and the air was coming out of the POA valve where I disconnected the muffler hose. I think that the poa valve is good according to the test I ran but I don't know whether this test is a good indicator of a healthy or busted POA valve.
Pondering my next move... The compressor sounds good (no noise that would alert me that something is wrong with it), no squealing from the belt, air blow great through the vents from low to high. As I stated in the beginning I had all new hoses, condenser and drier and had rebuilt the ac box and the POA valve was adjusted for R134. My mind is mush going through all the AC threads on the site, I need assistance - did I miss doing something? Should I have added more freon - higher than the 2.5 but lower than 3.2 lbs?
My original one and the one I received rebuilt (2016/2017?)
Is the POA valve calibrated for 134a? Pressure sounds good though, ought to freeze you out of there. How about the temp sensor bulb, mounted securely and wrapped with that goo the factory used?
Rule of thumb with a 134a conversion is use 75-80% of what the original R12 charge called for. As in if it wants 4lb of 12, use 3lb of 134a.
Good luck. AC can be a voodoo science sometimes.
*EDIT* Sorry, missed where you said POA was set for 134a.
Last edited by rocketraider; August 15th, 2020 at 05:17 AM.
Is the POA valve calibrated for 134a? Pressure sounds good though, ought to freeze you out of there. How about the temp sensor bulb, mounted securely and wrapped with that goo the factory used?
Rule of thumb with a 134a conversion is use 75-80% of what the original R12 charge called for. As in if it wants 4lb of 12, use 3lb of 134a.
Good luck. AC can be a voodoo science sometimes.
*EDIT* Sorry, missed where you said POA was set for 134a.
Okay, so I've had two cups of coffee and my mind is a bit clearer. I was re-reading the Service manual and came across the "Refrigeration Circuit" section, the mechanic had it backwards in how the system should work - he had me confused too. The system shows it goes from the compressor to the condenser to the drier to the expansion valve through the evaporator then into the POA valve before going back to the compressor. This means (to me) that the POA is acting correctly, I remember the mechanic pointing out that the expansion valve was warm too - so is it the expansion valve that is bad?
Last edited by tdhill01; August 15th, 2020 at 06:44 AM.
Tom, there is a replaceable screen in the expansion valve that gets clogged sometimes if the system breaks. Is the expansion valve new, used, original? A few years after our cars they went to an orifice screen deal. Scratch that...I see you said everything is new.
Last edited by mrolds69; August 15th, 2020 at 11:29 AM.
Tom, there is a replaceable screen in the expansion valve that gets clogged sometimes if the system breaks. Is the expansion valve new, used, original? A few years after our cars they went to an orifice screen deal. Scratch that...I see you said everything is new.
That's the thing bugging me - everything is new or rebuilt, I wasn't expecting any issues.
Tom, two of my old cars have AC, so I feel your pain. Everything new should make it easier, but even new parts can be bad. I'm not an expert, I have a 609 cert but little experience. I'll give it a thinking. Be aware a LOT of the AC stuff you see on youtube or read is incorrect. I mean a LOT, even the guys like Chris Fix, Eric's garage, they are kind of hacks, too. Almost nobody on those videos ever purges the hoses, etc.
Ok, a couple thoughts. The drier is new or NOS? An NOS drier might not be compatible with 134A. Does the drier have a sight glass? Have you looked at it with the A/C running? A 2.5 charge seems a bit low. What is the high and low pressure when it's running? The oil, usually within the system there is like an oz in the condenser, an ounce in the evaporator, so much in the hoses, and so much in compressor (most). Those numbers are in the manual for the total, I think. Because your system is "new" the 10.5 oz may be correct and I'm sure you checked. A lot of times the compressor would lug to start or "slug", but because you spun it first and it doesn't lug it should be ok. I assume your mechanic has a machine that recovers, vacs, measures, and charges? You definitely want some dye in the system for future probs. Typically, leaking is the biggest problem in an old system (not yours). You need to pull some pressure/temp charts off the net, so you have a good understanding of how temp affects pressures. It's been wicked hot here in MA as you know, and the pressures should be a lot higher, too. There is an AC forum on the net from AZ that usually has good info. Here's a quick pressure chart. Be aware humidity changes these numbers, too. https://www.jamcoautoparts.com/syste...shootingchart/
Last edited by mrolds69; August 15th, 2020 at 01:57 PM.
Ok, a couple thoughts. The drier is new or NOS? An NOS drier might not be compatible with 134A. Does the drier have a sight glass? Have you looked at it with the A/C running? A 2.5 charge seems a bit low. What is the high and low pressure when it's running? The oil, usually within the system there is like an oz in the condenser, an ounce in the evaporator, so much in the hoses, and so much in compressor (most). Those numbers are in the manual for the total, I think. Because your system is "new" the 10.5 oz may be correct and I'm sure you checked. A lot of times the compressor would lug to start or "slug", but because you spun it first and it doesn't lug it should be ok. I assume your mechanic has a machine that recovers, vacs, measures, and charges? You definitely want some dye in the system for future probs. Typically, leaking is the biggest problem in an old system (not yours). You need to pull some pressure/temp charts off the net, so you have a good understanding of how temp affects pressures. It's been wicked hot here in MA as you know, and the pressures should be a lot higher, too. There is an AC forum on the net from AZ that usually has good info. Here's a quick pressure chart. Be aware humidity changes these numbers, too. https://www.jamcoautoparts.com/syste...shootingchart/
The drier is new, I bought the parallel flow condenser and drier from Classic Auto Air. The drier does have a sight glass and it seams clear - no bubbles or such. I went low on the freon the second time to 2.5 lbs because the 3.2 lbs gave me the same problems. The original R12 Freon amount was 4 lbs and using 80% would bring it to 3.2 lbs of R134a. The mechanic had a Robinair add/recovery machine that used the High port to add and subtract the freon. The car was evacuated and then filled with R134a both times. I have pulled the charts that show the ambient temperatures and what type of readings will determine possible faults with the system. Thanks for the information about the AC forum. Even though I bought all these parts through the years all the openings for the hoses were always capped and nothing was open as far as I know to cause any contamination in the system. I'm going double check all connection and possibly take the compressor off of the car and empty its oil to see how much comes out to see if I have an issue there. I appreciate the input Frank.
When a system hasn't worked for a very long time, it's the worst thing. All the vacuum switches, the heater valve, the doors and actuators, there's just a lot of stuff you can't be sure about. You can test everything, then knock a vac hose off something and it messes things up. The tech, is he ASE, do you have confidence he knew what he was doing? It's pretty hard to mess up with a modern machine. You input the info, and it tells you just what to do. The charts will sometimes help because they may lead you in the right direction. I don't think it's a moisture problem or old parts problem. The v8buick.com forum I frequent has a section just for AC. It's weird because it should be putting out some amount of cooler air from the vents.
I see that you have all new parts and the open lines were capped off during the years the vehicle sat. I still wonder if there was something in the lines that blocked the expansion valve.
Why was the system dismantled back when?
Was the system ever flushed?
When a system hasn't worked for a very long time, it's the worst thing. All the vacuum switches, the heater valve, the doors and actuators, there's just a lot of stuff you can't be sure about. You can test everything, then knock a vac hose off something and it messes things up. The tech, is he ASE, do you have confidence he knew what he was doing? It's pretty hard to mess up with a modern machine. You input the info, and it tells you just what to do. The charts will sometimes help because they may lead you in the right direction. I don't think it's a moisture problem or old parts problem. The v8buick.com forum I frequent has a section just for AC. It's weird because it should be putting out some amount of cooler air from the vents.
I believe the guy is good and certified properly but he did tell me that he did not grow up working on these cars - the 80's cars was his gig. He did not know the term "POA" but he knew it was a valve, he also knew what he was doing when using the Robinair. I'm going to look into a couple of places on Monday in others nearby towns to see if I can find someone who is still knowledgeable with these cars.
I see that you have all new parts and the open lines were capped off during the years the vehicle sat. I still wonder if there was something in the lines that blocked the expansion valve.
Why was the system dismantled back when?
Was the system ever flushed?
Why was the system dismantled: when I got the car there was no ac hoses hooked up, no compressor, nothing except for the box that mounts to the firewall in the engine bay. You can see the condition of my old one in the photos I placed in this thread. I ended up dismantling everything - the car was basically stripped down as it was going off to the body shop but it still needed to be running. I had wanted to have the AC working when I finally completed the car so I decided to get all new/rebuilt parts. I took out the old ac box inside the engine bay and ordered a rebuilt one with the poa and expansion valves. I then went inside and took out the inside heater/ac box. I had the heater core sent out out to a radiator shop to get repaired as it was leaking. The box was not in great condition and I found a nicer one and went through that completely and placed the rebuilt heater core into the unit. The dash was completely taken apart and I went through the entire control system for the AC/Heater and all hoses were checked but I found no issue with any of them. I found all the controls to be working appropriately - the vents blew air when selected, the defroster vent blew air when selected and the heater vent blew air too. I drained the radiator that was in the car and replaced it with a new 4-core unit, I also replace the Heater Control Valve and all the hoses in the engine bay. I filled the new radiator with a 50/50 mix by Prestone - I did not flush the system because I did not feel I needed too.
Last edited by tdhill01; August 15th, 2020 at 10:00 PM.
Reason: grammatical correction
I was meaning did you flush the AC system. The cooling system has no bearing on your current AC issue.
After I wrote and re-read what I wrote I thought the same thing too - too tired. What I was getting at is that everything was replaced - completely taken apart... what would be left for me to do a flush unless you think there may have been a contaminate in the parts I put on? It make sense now thinking about it - thanks!
Question, on the inside AC/Heater box what is supposed to open to allow the evaporator to allow the cold air to come through into the compartment? I had taken off the lower ac vent and lower right side panel to view the side vent to see if it opened up properly when the lever was switched to the AC normal and Max settings and it worked properly.
I'm just trying to think of other reasons why the cold air is not making its way into the cabin. I truly appreciate the input given so far both through this thread and pm's.
Question, on the inside AC/Heater box what is supposed to open to allow the evaporator to allow the cold air to come through into the compartment? I had taken off the lower ac vent and lower right side panel to view the side vent to see if it opened up properly when the lever was switched to the AC normal and Max settings and it worked properly.
I'm just trying to think of other reasons why the cold air is not making its way into the cabin. I truly appreciate the input given so far both through this thread and pm's.
I found my answer looking at a Youtube video - I'm going to need to find out if the actuator is opening up the door to allow the AC to come into the cabin. Is there an easy way to check since it is behind the box?
Last edited by tdhill01; August 16th, 2020 at 08:38 AM.
Reason: added a question
Inside the HVAC box there is a door that moves to let air come from either the heater core or the evaporator. That door is controlled by a cable attached to the COOL / WARM slider control on the dash.
There is nothing inside the HVAC box that controls the flow of freon. The freon is all throughout the AC system, when the compressor runs it is moved through the system and the expansion valve creates a restriction so there is high pressure on one side and low pressure on the other. The low pressure freon goes through the evaporator where it absorbs heat from the air, then travels back to the compressor suction side.
I notice on all these forums for old cars, that there seems to be a lack of knowledge on old AC, cruise control, and convertible top systems. Ok, I knew what Kenneth meant right away, but like you it seems if it's all new, or rebuilt and capped, it would be ok. My biggest concern was that screen in the expansion valve. Like if you used your old valve, or had bought a used valve and maybe didn't check the screen. If it's as you say, then I can't see where flushing would be needed. The compressor oil is a prob maybe. The best way to drain them is standing it up from the hose holes. I know there's a plug, but I don't know if it gets all the oil out. I know ester is the universal oil, I don't know where you got the compressor from, and what was in it. I don't really know the effects of a small amount of oil left in the compressor. I know your system has run now, so if you drain the compressor you will know how much is in it. Then you can figure there is X in the evap, and X in the condenser, etc. I think that info is in the service manual. I think if you can find a good tech with a good machine, they can evacuate it and measure the oil and the refrigerant. I have an old Snap On r12 machine from maybe 2000 and it can do that. My cars are R12, I bought the machine cheap, but never really got it all up and running because I'm mostly just adding small amounts now and then. I'm concerned that your tech had never seen or worked on one system with a POA. There's got to be somebody around Milford, Franklin, Bellingham that does old cars. Maybe call Jimmy C (jcdynamic) and ask if he knows somebody.
Hindsight always being better, you should have vacuumed it yourself first, and tried to charge it yourself. Then you would know how to do it, because I can assure you later you will need to work on it again. Down south and out west, there are a lot of AC people. A lot of old trucks still have the old systems. The biggest problem is the recovery of the refrigerant when you are messing with them. But it's not the end of the world if you vent a little. You just don't want to invite all your neighbors over to watch!
Inside the HVAC box there is a door that moves to let air come from either the heater core or the evaporator. That door is controlled by a cable attached to the COOL / WARM slider control on the dash.
There is nothing inside the HVAC box that controls the flow of freon. The freon is all throughout the AC system, when the compressor runs it is moved through the system and the expansion valve creates a restriction so there is high pressure on one side and low pressure on the other. The low pressure freon goes through the evaporator where it absorbs heat from the air, then travels back to the compressor suction side.
okay, I appreciate the info. I found shop through another member where the guys are knowledgeable and I’ll bring it to them to hopefully figure it out.
I notice on all these forums for old cars, that there seems to be a lack of knowledge on old AC, cruise control, and convertible top systems. Ok, I knew what Kenneth meant right away, but like you it seems if it's all new, or rebuilt and capped, it would be ok. My biggest concern was that screen in the expansion valve. Like if you used your old valve, or had bought a used valve and maybe didn't check the screen. If it's as you say, then I can't see where flushing would be needed. The compressor oil is a prob maybe. The best way to drain them is standing it up from the hose holes. I know there's a plug, but I don't know if it gets all the oil out. I know ester is the universal oil, I don't know where you got the compressor from, and what was in it. I don't really know the effects of a small amount of oil left in the compressor. I know your system has run now, so if you drain the compressor you will know how much is in it. Then you can figure there is X in the evap, and X in the condenser, etc. I think that info is in the service manual. I think if you can find a good tech with a good machine, they can evacuate it and measure the oil and the refrigerant. I have an old Snap On r12 machine from maybe 2000 and it can do that. My cars are R12, I bought the machine cheap, but never really got it all up and running because I'm mostly just adding small amounts now and then. I'm concerned that your tech had never seen or worked on one system with a POA. There's got to be somebody around Milford, Franklin, Bellingham that does old cars. Maybe call Jimmy C (jcdynamic) and ask if he knows somebody.
Hindsight always being better, you should have vacuumed it yourself first, and tried to charge it yourself. Then you would know how to do it, because I can assure you later you will need to work on it again. Down south and out west, there are a lot of AC people. A lot of old trucks still have the old systems. The biggest problem is the recovery of the refrigerant when you are messing with them. But it's not the end of the world if you vent a little. You just don't want to invite all your neighbors over to watch!
Thanks Frank, I'm going to take the car down to a shop in Milford that I was told of by "My442" that should be able to find and fix the issue(s). You're right about trying to do it myself so I have a better understanding of the process as I have no intention of selling this car - hoping to pass it on when the time comes to one of the kids.
Last edited by tdhill01; August 25th, 2020 at 12:33 AM.
Is evaporator new or did you reuse the old one. Could possibly have been some crap in there that got stirred up when system started circulating refrigerant? And it's possible you just got a bum POA valve.
AC and especially cruise were expensive options back in the day and didn't get ordered often here. Those old Dana Perfect Circle motor-driven units were complex to repair too. Add in the few service techs who did work on and understand these things are in their 80s and often don't do computers... but boy could they augment their retirement if they were still up to working on some of these gadgets.
Last edited by rocketraider; August 16th, 2020 at 01:43 PM.
Is evaporator new or did you reuse the old one. Could possibly have been some crap in there that got stirred up when system started circulating refrigerant? And it's possible you just got a bum POA valve.
AC and especially cruise were expensive options back in the day and didn't get ordered often here. Those old Dana Perfect Circle motor-driven units were complex to repair too. Add in the few service techs who did work on and understand these things are in their 80s and often don't do computers... but boy could they augment their retirement if they were still up to working on some of these gadgets.
The evaporated is new, I hope the POA is still good - crossing fingers that it something minor I need to fix. I wish I was one of these guys who know these car inside and out - could make some good walking around money while enjoying retirement life.
I finally have AC! Just in time for summer to come and go It was the POA that was defective, I bought another to replace it only to have the guy ship me the wrong style. The second one that he sent fixed the issue I was having, now I'm set for next summer's heat
August 14th, 2020, 09:16 PM
It was the POA that was defective, I bought another to replace it only to have the guy ship me the wrong style. The second one that he sent fixed the issue I was having, now I'm set for next summer's heat 
