[C2] A/C - Questions about R12 to R134A conversion
10-16-2018, 03:35 PM
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A/C - Questions about R12 to R134A conversion
I had the factory A/C in my 67 coupe converted over to R134A back in June. After getting the car back I was pleased the A/C cooled much better. Some time later while cleaning under the hood I noticed that the old drier was still in place. I checked the invoice from the shop and saw it included a charge for "replacing A/C drier". It was obvious why they hadn't replaced it - the hood must come off to get to the drier. I called the shop back and they promised to make good and replace the original drier at no extra cost. The tech said the old drier isn't necessarily compatible with R134A, and because its age is unknown, should be replaced. So I'm taking the car back this Friday. They'll be replacing the drier and re-charging the system. In another post, I asked for and got great tips on how to safely remove the hood.
After the conversion in June the A/C blew pretty cold. The shop did not replace the stock hoses, saying the system held its charge very well during their test. I stuck a thermometer in the passenger outlet and got about 45 F after the work was done. That isn't the 38-40 F that the stock system is supposed to put out, but I was happy as it was much better than the minimal cooling I got before. I also heard that R-134A doesn't cool quite as well as did the old Freon R12 could. I've noticed a gradual deterioration in cooling since June, with outlet temps now closer to 50-52 F. Would this be due to the old drier being clogged? The shop didn't touch the POA valve, saying "it should be fine". Should anything be done to the stock POA valve?
Could I have damaged the compressor by running that old drier all summer? Note I've only run the A/C for maybe 10 hours since it was converted, as I don't drive the car that much, and only run the A/C maybe a quarter of the time.
Any tips/ideas/feedback on this before I take the car back to the shop on Friday would be much appreciated.
After the conversion in June the A/C blew pretty cold. The shop did not replace the stock hoses, saying the system held its charge very well during their test. I stuck a thermometer in the passenger outlet and got about 45 F after the work was done. That isn't the 38-40 F that the stock system is supposed to put out, but I was happy as it was much better than the minimal cooling I got before. I also heard that R-134A doesn't cool quite as well as did the old Freon R12 could. I've noticed a gradual deterioration in cooling since June, with outlet temps now closer to 50-52 F. Would this be due to the old drier being clogged? The shop didn't touch the POA valve, saying "it should be fine". Should anything be done to the stock POA valve?
Could I have damaged the compressor by running that old drier all summer? Note I've only run the A/C for maybe 10 hours since it was converted, as I don't drive the car that much, and only run the A/C maybe a quarter of the time.
Any tips/ideas/feedback on this before I take the car back to the shop on Friday would be much appreciated.
10-16-2018, 08:44 PM
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Mr. Fufu:
If it so called "blows cold" and has for 30 days I'd leave it alone. Don't open the system up needlessly. There is no such thing as a normal output temperatures such as 40 degrees - only a chart of temperature ranges graphed against ambient temperature and humidity. A refrigeration system is evaluated on the basis of system pressures, high side and low side, ambient temperature at the condenser, and then evaporator temperature.
When you want to know what's up with your air conditioner you want to put the gauges on it, these tell all, and a whole lot more than a turkey roasting thermometer in the dash vent.
When you open a system for anything more than repair time, say hours, the dryer should be changed/re-filled . If the system is being converted to 134A you want to at least remove and drain the dryer before doing so to avoid mixing dissimilar oil and over fill.
Dan
If it so called "blows cold" and has for 30 days I'd leave it alone. Don't open the system up needlessly. There is no such thing as a normal output temperatures such as 40 degrees - only a chart of temperature ranges graphed against ambient temperature and humidity. A refrigeration system is evaluated on the basis of system pressures, high side and low side, ambient temperature at the condenser, and then evaporator temperature.
When you want to know what's up with your air conditioner you want to put the gauges on it, these tell all, and a whole lot more than a turkey roasting thermometer in the dash vent.
When you open a system for anything more than repair time, say hours, the dryer should be changed/re-filled . If the system is being converted to 134A you want to at least remove and drain the dryer before doing so to avoid mixing dissimilar oil and over fill.
Dan
Last edited by dplotkin; 10-16-2018 at 08:45 PM.
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Mr Fufu (10-17-2018)
10-17-2018, 01:51 PM
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It seems that a LOT of people feel it is necessary to convert from R12 to 134, but so far, I have not seen the need. All my older cars still have R12 and they cool fine. My latest is a 70 Chevelle convertible which came with factory air cond. It worked when I bought it in 98, but not great, and I did a fair amount of servicing to get it working. Never was satisfactory. Several of my friends with Chevelles recommended removing the system and sending it to Classic Auto Air in Tampa, FL. I did. They TOTALLY rebuilt the system (including rebuilding the POA valve and expansion valve), replated everything and shipped it back to me with a new dryer. I replaced the main hose/manifold between the compressor and AC unit, flushed everything else, dried out the system, put it on a vac pump for 18hrs, turned off the pump and let it sit for 6hrs. Gauge NEVER moved. Charged it with R12 -------------------------------- and it still puts out 38-40deg in the summer!!!
Oh ya, I still have 2 1/2 30lb bottles of R12 and one case of cans, so I'm good for a while.
Also, my ugly, rusty, POS 51 Chevy has a VERY old under dash AC unit and an antique York style compressor which still puts out COLD R12 air. That system has not been open for about 25yrs and in that time it has had about 1 can of R12 added.
It will be VERY difficult to convince me to convert any of my cars to 134.
Oh ya, I still have 2 1/2 30lb bottles of R12 and one case of cans, so I'm good for a while.
Also, my ugly, rusty, POS 51 Chevy has a VERY old under dash AC unit and an antique York style compressor which still puts out COLD R12 air. That system has not been open for about 25yrs and in that time it has had about 1 can of R12 added.
It will be VERY difficult to convince me to convert any of my cars to 134.
Last edited by DZAUTO; 10-17-2018 at 01:54 PM.
10-17-2018, 02:03 PM
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The conversion should cool just about as good, or as good as the original. The receiver/dryer is a dessicant canister that traps moisture and contaminants. It is similar to an oil filter in an oil system. It is ALWAYS replaced any time the system is opened up. Running an old receiver/dryer is like changing the engine oil and leaving the dirty filter in place. My vote is to get the dryer replaced, and have the system evacuated and re-charged. You need things clean and dry in the system.....moisture will prevent optimal cooling.
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Mr Fufu (10-17-2018)
10-17-2018, 05:11 PM
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Thanks for your advice, guys.
I'll ask the shop to evacuate and recharge the system once they've replaced the drier.
Is there anything I should know about the POA valve? My car still has the stock one. I don't know if it was replaced in the past. Will the system work fine with the stock POA valve after the conversion to R134A? Or is there some adjustment that needs to be made to the POA valve? I don't know if these are adjustable. How would I know if the POA goes bad?
I'll ask the shop to evacuate and recharge the system once they've replaced the drier.
Is there anything I should know about the POA valve? My car still has the stock one. I don't know if it was replaced in the past. Will the system work fine with the stock POA valve after the conversion to R134A? Or is there some adjustment that needs to be made to the POA valve? I don't know if these are adjustable. How would I know if the POA goes bad?
10-17-2018, 06:47 PM
#6
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I believe there are more misconceptions and old wives tales about refergeration (AC) than any other automotive component.
The receiver drier is not similar to an oil filter. It might have a screen or bag to catch marbles, but it is to hold excess refrigerant so liquid does not enter the compressor. It contains a bag of chemical desiccant to adsorb any moisture in the system liquid. If left under vacuum long enough with a little heat, it will release the moisture and can be reused. If a closed system is contaminated, you replace it to get red of the metal shavings. It does not wear out unless the desiccant bag is damaged.
The receiver drier is not similar to an oil filter. It might have a screen or bag to catch marbles, but it is to hold excess refrigerant so liquid does not enter the compressor. It contains a bag of chemical desiccant to adsorb any moisture in the system liquid. If left under vacuum long enough with a little heat, it will release the moisture and can be reused. If a closed system is contaminated, you replace it to get red of the metal shavings. It does not wear out unless the desiccant bag is damaged.
10-17-2018, 07:11 PM
#7
Melting Slicks
My only concern with a conversion is removal of the mineral oil. I had a bad experience recently when I bought my 69 Camaro.
AC worked a few times then started to fade. I decided to pull it all apart and found that whoever converted it did not properly flush the mineral oil. Once I drained it, I had a cup of oil that didn’t mix. I ended up flushing the system myself, replacing the hoses / o-rings, receiver/drier, and rebuilding the compressor. Went back to R12 and everything is great.
Ed
AC worked a few times then started to fade. I decided to pull it all apart and found that whoever converted it did not properly flush the mineral oil. Once I drained it, I had a cup of oil that didn’t mix. I ended up flushing the system myself, replacing the hoses / o-rings, receiver/drier, and rebuilding the compressor. Went back to R12 and everything is great.
Ed
10-17-2018, 09:46 PM
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It is utter nonsense, by the way, that 134A performs less well than R12 when charged properly into an otherwise sound operating system. I run it in a 62 Bonneville STV system and a 68 Chrysler RV2/EPR system that if anything over-cool. The reason to convert is cost and convenience. The refrigerant costs less and is widely available from techs who have the equipment and knowledge to use it. If you have to empty a system I wouldn't put 12 back in, there is no performance advantage. But an intact 12 system that occasionally needs topping off? I've had two of those for the last 18 years.
Dan
Last edited by dplotkin; 10-17-2018 at 09:48 PM.
10-17-2018, 11:24 PM
#9
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My only concern with a conversion is removal of the mineral oil. I had a bad experience recently when I bought my 69 Camaro.
AC worked a few times then started to fade. I decided to pull it all apart and found that whoever converted it did not properly flush the mineral oil. Once I drained it, I had a cup of oil that didn’t mix. I ended up flushing the system myself, replacing the hoses / o-rings, receiver/drier, and rebuilding the compressor. Went back to R12 and everything is great.
Ed
AC worked a few times then started to fade. I decided to pull it all apart and found that whoever converted it did not properly flush the mineral oil. Once I drained it, I had a cup of oil that didn’t mix. I ended up flushing the system myself, replacing the hoses / o-rings, receiver/drier, and rebuilding the compressor. Went back to R12 and everything is great.
Ed
What I did with my previously converted system was to remove and fully drain the compressor, refill it with mineral oil, rebuild my STV, blow out the evap and condenser with nitrogen @50 psig, clean screen filter at expansion valve inlet, replace drier/receiver, replace all o-rings, check for leaks, draw a deep vacuum, and recharge with R12. (Thanks again to Powershift
)The question regarding adjustment of a POA valve I can't shed any light on, because mine is a 65 and uses the STV. STV has a diaphragm which eventually needs replacing, and the valve should be readjusted if converting from R12 to R134.
My other concern would be with the shop OP is using to service the system. If they billed for replacing the drier but didn't do the job, that would be a huge red flag to me. It'd be tough to trust anything that they said after pulling that stunt. Maybe better off taking it elsewhere?
10-17-2018, 11:29 PM
#10
Melting Slicks
Powershift helped me as wel!! I too would be concerned with a shop that didn’t replace the drier. It would make me question everything they did especially if I was having a problem.
Id recommend you ask them to tell you everything they did to covert over with a focus on flushing the entire system.
Good of luck and keep us posted.
Ed
Id recommend you ask them to tell you everything they did to covert over with a focus on flushing the entire system.
Good of luck and keep us posted.
Ed
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Mr Fufu (10-19-2018)
10-17-2018, 11:34 PM
#11
Melting Slicks
“The tech said the old drier isn't necessarily compatible with R134A, and because its age is unknown, should be replaced“
Not sure what this means.
1. Anytime you open a system the drier needs to be replaced.
2. A factory drier will work with both r12 and r134.
3. You shouldn’t take a drier that was used with r12 and reuse it with r134. I’d be worried about oil contamination
The POA should be adjusted for r134 to optimize the performance. Most shops don’t know how to do it hence tell you it’s ok.
Ed
Not sure what this means.
1. Anytime you open a system the drier needs to be replaced.
2. A factory drier will work with both r12 and r134.
3. You shouldn’t take a drier that was used with r12 and reuse it with r134. I’d be worried about oil contamination
The POA should be adjusted for r134 to optimize the performance. Most shops don’t know how to do it hence tell you it’s ok.
Ed
Last edited by emdoller; 10-17-2018 at 11:36 PM.
10-18-2018, 09:58 AM
#12
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“The tech said the old drier isn't necessarily compatible with R134A, and because its age is unknown, should be replaced“
Not sure what this means.
1. Anytime you open a system the drier needs to be replaced.
2. A factory drier will work with both r12 and r134.
3. You shouldn’t take a drier that was used with r12 and reuse it with r134. I’d be worried about oil contamination
The POA should be adjusted for r134 to optimize the performance. Most shops don’t know how to do it hence tell you it’s ok.
Ed
Not sure what this means.
1. Anytime you open a system the drier needs to be replaced.
2. A factory drier will work with both r12 and r134.
3. You shouldn’t take a drier that was used with r12 and reuse it with r134. I’d be worried about oil contamination
The POA should be adjusted for r134 to optimize the performance. Most shops don’t know how to do it hence tell you it’s ok.
Ed
Automotive driers sold today contain the desiccant XH7. This is a zeolite/molecular sieve desiccant which is good for both R12 and R134a and their respective oils/lubricants. It was not always this way. Prior to around 1990 (or so) automotive driers contains the desiccant 4AXH-5 which had been developed specifically for R12/R22 refrigerants. When used for R134a they began to break down and form acids, fines and sludge. UOP (Universal Oil Products) then developed a different desiccant that could be used for both. This is the XH7.
So the desiccant in original 1967 HARRISON/DELCO driers will fail if the refrigerant is changed to R134a.
Larry
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Mr Fufu (10-19-2018)
10-18-2018, 01:30 PM
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Perhaps the oil filter analogy was a poor one, but regardless, the receiver/dryer should be replaced every time the system is opened. It's industry standard, and has been for decades.
10-18-2018, 09:45 PM
#14
Melting Slicks
Ed:
Automotive driers sold today contain the desiccant XH7. This is a zeolite/molecular sieve desiccant which is good for both R12 and R134a and their respective oils/lubricants. It was not always this way. Prior to around 1990 (or so) automotive driers contains the desiccant 4AXH-5 which had been developed specifically for R12/R22 refrigerants. When used for R134a they began to break down and form acids, fines and sludge. UOP (Universal Oil Products) then developed a different desiccant that could be used for both. This is the XH7.
So the desiccant in original 1967 HARRISON/DELCO driers will fail if the refrigerant is changed to R134a.
Larry
Automotive driers sold today contain the desiccant XH7. This is a zeolite/molecular sieve desiccant which is good for both R12 and R134a and their respective oils/lubricants. It was not always this way. Prior to around 1990 (or so) automotive driers contains the desiccant 4AXH-5 which had been developed specifically for R12/R22 refrigerants. When used for R134a they began to break down and form acids, fines and sludge. UOP (Universal Oil Products) then developed a different desiccant that could be used for both. This is the XH7.
So the desiccant in original 1967 HARRISON/DELCO driers will fail if the refrigerant is changed to R134a.
Larry
Ed
10-19-2018, 04:13 PM
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Mr FuFU,
It won't hurt the compressor. Never found one that was converted to 134 with bad case O-rings. All the ceramic seals I buy have a black O-ring that contacts the shaft. I now change them to the green. Pictures show green but they are delivered black and distorted by the spring pressure. Conversion kits do not replace the inner O-rings.
There is also a oil that is compatible with mineral.
Dom
It won't hurt the compressor. Never found one that was converted to 134 with bad case O-rings. All the ceramic seals I buy have a black O-ring that contacts the shaft. I now change them to the green. Pictures show green but they are delivered black and distorted by the spring pressure. Conversion kits do not replace the inner O-rings.
There is also a oil that is compatible with mineral.
Dom
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Mr Fufu (10-22-2018)
10-19-2018, 06:18 PM
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Ed:
Automotive driers sold today contain the desiccant XH7. This is a zeolite/molecular sieve desiccant which is good for both R12 and R134a and their respective oils/lubricants. It was not always this way. Prior to around 1990 (or so) automotive driers contains the desiccant 4AXH-5 which had been developed specifically for R12/R22 refrigerants. When used for R134a they began to break down and form acids, fines and sludge. UOP (Universal Oil Products) then developed a different desiccant that could be used for both. This is the XH7.
So the desiccant in original 1967 HARRISON/DELCO driers will fail if the refrigerant is changed to R134a.
Larry
Automotive driers sold today contain the desiccant XH7. This is a zeolite/molecular sieve desiccant which is good for both R12 and R134a and their respective oils/lubricants. It was not always this way. Prior to around 1990 (or so) automotive driers contains the desiccant 4AXH-5 which had been developed specifically for R12/R22 refrigerants. When used for R134a they began to break down and form acids, fines and sludge. UOP (Universal Oil Products) then developed a different desiccant that could be used for both. This is the XH7.
So the desiccant in original 1967 HARRISON/DELCO driers will fail if the refrigerant is changed to R134a.
Larry
10-22-2018, 06:39 PM
#17
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This would be my concern as well. Whenever an R12 to R134 conversion has been done by a PO, it's impossible to know for sure if the original mineral oil was totally flushed from the system, if it was replaced with PAG (R12 incompatible) or ester (compatible) oil, if o-rings were changed, and other unknown questionable procedures.
What I did with my previously converted system was to remove and fully drain the compressor, refill it with mineral oil, rebuild my STV, blow out the evap and condenser with nitrogen @50 psig, clean screen filter at expansion valve inlet, replace drier/receiver, replace all o-rings, check for leaks, draw a deep vacuum, and recharge with R12. (Thanks again to Powershift)
The question regarding adjustment of a POA valve I can't shed any light on, because mine is a 65 and uses the STV. STV has a diaphragm which eventually needs replacing, and the valve should be readjusted if converting from R12 to R134.
My other concern would be with the shop OP is using to service the system. If they billed for replacing the drier but didn't do the job, that would be a huge red flag to me. It'd be tough to trust anything that they said after pulling that stunt. Maybe better off taking it elsewhere?
What I did with my previously converted system was to remove and fully drain the compressor, refill it with mineral oil, rebuild my STV, blow out the evap and condenser with nitrogen @50 psig, clean screen filter at expansion valve inlet, replace drier/receiver, replace all o-rings, check for leaks, draw a deep vacuum, and recharge with R12. (Thanks again to Powershift
)The question regarding adjustment of a POA valve I can't shed any light on, because mine is a 65 and uses the STV. STV has a diaphragm which eventually needs replacing, and the valve should be readjusted if converting from R12 to R134.
My other concern would be with the shop OP is using to service the system. If they billed for replacing the drier but didn't do the job, that would be a huge red flag to me. It'd be tough to trust anything that they said after pulling that stunt. Maybe better off taking it elsewhere?