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  #1  
Old 05-12-2019, 12:16 PM
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question regarding a/c compressor oil/designation

A couple of years ago I put a Rollguy Sanden system on a w123 including the fan run when a/c on option. I left the car r12. Now it is back in in the shop. With the correct amount of r12 I'm getting vacuum on the lo side of compressor and 150 or so on hi side (ambient 75dF). No cold air, site glass is clear with plenty of air blowing out the dash vents.

My question is, when I got compressor it stated for r134. I worked with the assumption that if I flushed compressor out I could convert it to mineral oil for the r12 operation. Was this a good assumption or no?

I'm still nosing around on this one. I will probably end up getting a p-flow condenser and convert to r134.
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Old 05-12-2019, 12:54 PM
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Sounds like you have a clog in the system or the expansion valve is pinched off/stuck. The compressor is the same for R12 or R134a, it's just what kind of oil it came with. If you use POE or PAO oil, you can run either refrigerant. Mineral oil is only for R12, PAG is only for R134a. POE or PAO are "universal".
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Old 05-12-2019, 11:59 PM
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Save yourself the trouble and just use r152a. I'm coming up on my second summer with it and I'm still getting 20F sometime less at the vents.
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Old 05-13-2019, 09:21 AM
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Originally Posted by lsmalley View Post
Save yourself the trouble and just use r152a. I'm coming up on my second summer with it and I'm still getting 20F sometime less at the vents.
You have a control problem or you're full of it. The A/C system has a control in it to prevent the coil from freezing. Older cars were a fluid filled probe with a set of mechanical contacts, newer cars used a thermistor poked in the plenum next to the coil to shut the compressor off when the coil reached ~38˚F. Letting the coil freeze lets all the condensation it's pulling out of the air freeze to it, forming a massive block of ice. Then your cooling stops and you defeated the purpose of having A/C.
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The Diseasel Thread - Everything You Didn't Know You Wanted To Know
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Old 05-13-2019, 11:15 AM
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Originally Posted by engatwork View Post
A couple of years ago I put a Rollguy Sanden system on a w123 including the fan run when a/c on option. I left the car r12. Now it is back in in the shop. With the correct amount of r12 I'm getting vacuum on the lo side of compressor and 150 or so on hi side (ambient 75dF). No cold air, site glass is clear with plenty of air blowing out the dash vents.

My question is, when I got compressor it stated for r134. I worked with the assumption that if I flushed compressor out I could convert it to mineral oil for the r12 operation. Was this a good assumption or no?

I'm still nosing around on this one. I will probably end up getting a p-flow condenser and convert to r134.
vacuum on low side and 150 on high. - thats very strange. A clog would have caused an overpressure on the high side. Do a first test of replacing the expansion valve with a new one.
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Old 05-13-2019, 03:22 PM
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Originally Posted by Diseasel300 View Post
You have a control problem or you're full of it. The A/C system has a control in it to prevent the coil from freezing. Older cars were a fluid filled probe with a set of mechanical contacts, newer cars used a thermistor poked in the plenum next to the coil to shut the compressor off when the coil reached ~38˚F. Letting the coil freeze lets all the condensation it's pulling out of the air freeze to it, forming a massive block of ice. Then your cooling stops and you defeated the purpose of having A/C.
I can create a video of my fully functioning a/c showing temps at the vent. I have several threads on the forum following the trouble I had with my system and the conversion to 152a with photos of the temp readings. I'm not on the forum to deceive any of the members. From my personal experience, this is a much better way to go. I live in southern California (desert) so the summers are brutal and this has been the best my ac has ever been. This way also provides you with not only superior cooling, but the cost of the cans (like 6 20 oz cans for $12, or something) is extremely affordable and no strict laws governing the release of the r152a. The added bonus is that right now OP is experiencing a problem in the system and unless he has 2 separate machines to evacuate (r12 and r134) to avoid contamination of either, then the cost of troubleshooting is high. Whereas with the r152a you can simply clear your system, address the component which you believe has failed, and then vacuum out the air and refill. Even if the problem wasn't resolved, the price of the r152a makes the troubleshooting easier without worrying about the cost of your refrigerant and having it properly evacuated.
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Old 05-13-2019, 03:33 PM
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I don't care about your temps at the vent. If you live anywhere except a desert with 0-10% humidity, you'll be experiencing an iced coil with those kinds of vent temps. I'm speaking from experience here, not just heresay.

R134a is the same cost or cheaper than R152a and on a properly charged and functioning system cools just as good if not better than R152a (especially at idle where R152a struggles). Last summer with it being 109˚ in the summer here, my SDL's A/C was blowing a cool 38˚ at the vents running on 134a and the completely stock system. When set up properly and charged by someone who knows what they're doing, it works just fine.
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Old 05-13-2019, 03:46 PM
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Originally Posted by Diseasel300 View Post
R134a is the same cost or cheaper than R152a...
Where? 18 oz can of r134a is like $43+ which includes a $10 core. Either way, OP will hopefully get his a/c functioning properly and can consider his options.
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Old 05-13-2019, 03:57 PM
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Maybe in California? It's $4.12 for a 12 oz can here at Wal-Mart. I just bought some this last weekend to service the leaking Honda's A/C.
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