66-late early-67 and up GM POA and other AC info.
September 14th, 2015, 10:55 AM
#1
CH3NO2 LEARN IT BURN IT
Thread Starter
Join Date: Jul 2010
Location: Land of Taxes
Posts: 4,846
66-late early-67 and up GM POA and other AC info.
Dan, Pat, Joe, Eric etc......If this post doesn't belong here please move it maybe to its own POA valve adjustment sticky. If you even think its worthy? Feel free to edit this.
Thought this would be a good Sticky? I see the POA Sticky on the general page is for 72 only but this one covers late 66 to late 73. Not sure after mid to late 73. Id assume anything with an R12 system using a POA wanting to convert to 134a. It applies to most GM vehicles from about 66-67 and up with a POA valve system not an STV system (suction throttle valve) found on 66-67 and earlier cars. Much of this excerpt is taken from "Corvette forum dot com" a few years ago so the pricing is likely obsolete by now.
This is not the bible on AC and I'm not an expert but do have advanced automotive AC knowledge, especially the old school stuff. I have often called the guys from either classic or vintage auto air for help. Both are great and willing to freely give out knowledge. Now they both can retro fit an old non working POA with a 134a orifice kit using the original POA body for those who dont want to install the retro fit valve and retain the OEM look. They will also calibrate a R12 POA to 134a for you verses guessing. I have performed the adjustment noted below in a good system with restored hoses, dryer, o-rings, correct oil etc.... It works great. Steve
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Retrofitting to R134A
With R12 production halted it is not a question of if but when your old AC system will have to be converted to the new R134A refrigerant. Besides, you cannot legally purchase R12 without a special license so if you want to do your own AC work, you have to get R134A.
There is a lot of talk of R134A retrofitted systems not cooling well, but if the conversion is done right there is no noticeable loss in cooling capacity. Actually, after I did my conversion and especially after doing the POA valve adjustment described below, I reach 43F vent temperatures on a 90 degree day. The service manual lists 49F-52F as normal, so I'm outperforming the original R12 system with my retrofit!
The process of converting to R134A is not terribly complicated, but there are a few things to keep in mind:
Hoses. R134A consists of smaller molecules than R12. This means it will leak easier. Hoses should preferably be of the barrier type. However, it has shown that older hoses perform ok after they have been used with R12. The R12 impregnates the rubber and acts as a barrier for the R134A.
Oil. R12 systems use 500 viscosity mineral oil. R134A systems use PAG oil. The two are not compatible. If mineral oil is used with R134A, it will not mix with the refrigerant, and the compressor will starve for oil and seize. Fortunately there are solutions. Ester oil is compatible with both PAG and mineral oil. Furthermore, there are additives available that will make the old mineral oil in the system mix with R134A.
Fittings. R134A uses new fittings of the quick-connect type. Fitting adapters are available that will screw onto the old R12 fittings.
O-rings. To minimize the chance of leaks, the new blue O-rings should be used. The older black O-rings used with R12 may promote leaks.
Receiver-Drier. The receiver dryer should always be replaced when the system has been opened. Be sure to get a receiver-dryer that is compatible with R134A. Most receiver-dryers available today will be compatible with both R12 and R134A.
POA Valve adjustment. The POA Valve regulates the pressure inside the Evaporator. It is set for R12's optimum pressure of 29.5 PSI. To get maximum efficiency from R134A it has to be adjusted for a lower pressure. Looking into the inlet of the valve (through the fitting where the hose to the Evaporator goes), an adjustment screw with a locknut can be seen. Loosen the locknut and turn the adjustment 1/4 turn counter-clockwise. This adjustment lowered my vent temperatures from 52F to 43F on a 90F day!
Below are the things I got to get the AC in my '71 Corvette operational. The system had been open for several years, damaging the expansion and POA valve as well as depositing dirt and sludge in the evaporator and condenser. If your system is in good shape, some of the items below are not necessary.
1... Rebuilt compressor (Autozone $55).
2... Expansion Valve (Autozone $29).
3... Receiver-Dryer, R134A compatible (Autozone $29).
4... POA Valve (NAPA $67).
5... Quest R12 to R134A conversion kit containing oil additive and fittings (Autozone $25).
6... 2 high side adapter fittings. The high side fitting in the kit didn't work and an additional fitting was needed for the POA valve diagnostic fitting (Autozone $5).
7... Blue O-ring assortment (Autozone $5).
8... 2oz Ester oil charge (Autozone $4).
9... 4 12oz cans of R134A (NAPA $4 each).
10... AC insulation used to insulate the Expansion valve probe (NAPA $20).
The first step was to flush the evaporator and condenser. After the flush, I installed the compressor, expansion valve, POA valve (see POA valve adjustment above), Receiver-Dryer and fitting adapters. I used blue O-rings to minimize leaks. The expansion valve temperature probe has to be insulated using special AC insulation material.
Next I connected the gauges and pulled a vacuum for 1 hour, and then connected a 12oz can of R134A. The engine has to be running to get all the R134A in the can into the engine. After the first can I added the 2oz oil charge to replace the oil that was lost during flushing. I then added another 2 1/2 cans for a total of 3 1/2 cans, or 42oz. The pressures were 260/30 on a 90F day. Note that the pressures change drastically depending on ambient temperature and condenser temperature. On a 70F day, you should look for around 180-220 high side and 20-30 low. You might also have to elevate the idle to 1000-1200 to get accurate readings.
Thought this would be a good Sticky? I see the POA Sticky on the general page is for 72 only but this one covers late 66 to late 73. Not sure after mid to late 73. Id assume anything with an R12 system using a POA wanting to convert to 134a. It applies to most GM vehicles from about 66-67 and up with a POA valve system not an STV system (suction throttle valve) found on 66-67 and earlier cars. Much of this excerpt is taken from "Corvette forum dot com" a few years ago so the pricing is likely obsolete by now.
This is not the bible on AC and I'm not an expert but do have advanced automotive AC knowledge, especially the old school stuff. I have often called the guys from either classic or vintage auto air for help. Both are great and willing to freely give out knowledge. Now they both can retro fit an old non working POA with a 134a orifice kit using the original POA body for those who dont want to install the retro fit valve and retain the OEM look. They will also calibrate a R12 POA to 134a for you verses guessing. I have performed the adjustment noted below in a good system with restored hoses, dryer, o-rings, correct oil etc.... It works great. Steve
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Retrofitting to R134A
With R12 production halted it is not a question of if but when your old AC system will have to be converted to the new R134A refrigerant. Besides, you cannot legally purchase R12 without a special license so if you want to do your own AC work, you have to get R134A.
There is a lot of talk of R134A retrofitted systems not cooling well, but if the conversion is done right there is no noticeable loss in cooling capacity. Actually, after I did my conversion and especially after doing the POA valve adjustment described below, I reach 43F vent temperatures on a 90 degree day. The service manual lists 49F-52F as normal, so I'm outperforming the original R12 system with my retrofit!
The process of converting to R134A is not terribly complicated, but there are a few things to keep in mind:
Hoses. R134A consists of smaller molecules than R12. This means it will leak easier. Hoses should preferably be of the barrier type. However, it has shown that older hoses perform ok after they have been used with R12. The R12 impregnates the rubber and acts as a barrier for the R134A.
Oil. R12 systems use 500 viscosity mineral oil. R134A systems use PAG oil. The two are not compatible. If mineral oil is used with R134A, it will not mix with the refrigerant, and the compressor will starve for oil and seize. Fortunately there are solutions. Ester oil is compatible with both PAG and mineral oil. Furthermore, there are additives available that will make the old mineral oil in the system mix with R134A.
Fittings. R134A uses new fittings of the quick-connect type. Fitting adapters are available that will screw onto the old R12 fittings.
O-rings. To minimize the chance of leaks, the new blue O-rings should be used. The older black O-rings used with R12 may promote leaks.
Receiver-Drier. The receiver dryer should always be replaced when the system has been opened. Be sure to get a receiver-dryer that is compatible with R134A. Most receiver-dryers available today will be compatible with both R12 and R134A.
POA Valve adjustment. The POA Valve regulates the pressure inside the Evaporator. It is set for R12's optimum pressure of 29.5 PSI. To get maximum efficiency from R134A it has to be adjusted for a lower pressure. Looking into the inlet of the valve (through the fitting where the hose to the Evaporator goes), an adjustment screw with a locknut can be seen. Loosen the locknut and turn the adjustment 1/4 turn counter-clockwise. This adjustment lowered my vent temperatures from 52F to 43F on a 90F day!
Below are the things I got to get the AC in my '71 Corvette operational. The system had been open for several years, damaging the expansion and POA valve as well as depositing dirt and sludge in the evaporator and condenser. If your system is in good shape, some of the items below are not necessary.
1... Rebuilt compressor (Autozone $55).
2... Expansion Valve (Autozone $29).
3... Receiver-Dryer, R134A compatible (Autozone $29).
4... POA Valve (NAPA $67).
5... Quest R12 to R134A conversion kit containing oil additive and fittings (Autozone $25).
6... 2 high side adapter fittings. The high side fitting in the kit didn't work and an additional fitting was needed for the POA valve diagnostic fitting (Autozone $5).
7... Blue O-ring assortment (Autozone $5).
8... 2oz Ester oil charge (Autozone $4).
9... 4 12oz cans of R134A (NAPA $4 each).
10... AC insulation used to insulate the Expansion valve probe (NAPA $20).
The first step was to flush the evaporator and condenser. After the flush, I installed the compressor, expansion valve, POA valve (see POA valve adjustment above), Receiver-Dryer and fitting adapters. I used blue O-rings to minimize leaks. The expansion valve temperature probe has to be insulated using special AC insulation material.
Next I connected the gauges and pulled a vacuum for 1 hour, and then connected a 12oz can of R134A. The engine has to be running to get all the R134A in the can into the engine. After the first can I added the 2oz oil charge to replace the oil that was lost during flushing. I then added another 2 1/2 cans for a total of 3 1/2 cans, or 42oz. The pressures were 260/30 on a 90F day. Note that the pressures change drastically depending on ambient temperature and condenser temperature. On a 70F day, you should look for around 180-220 high side and 20-30 low. You might also have to elevate the idle to 1000-1200 to get accurate readings.
Thread
Thread Starter
Forum
Replies
Last Post
