Obsessing over my AC 134 conversion

[PbFut]

Those of you that have read my past post by now know I tend to obsess over stupid little things. It’s a bad habit but like an itch difficult (for me) to satisfy. I’ve never performed service on a AC before so I’ve been reading up. I have a couple simple questions I can’t find a definitive answer for.
Key points. The system is an original 1972 R12. Air handler fan and vents clean and heater works very well and blows hard. I will be verifying the POA valve is working and recalibrate to the recommended pressure. I will retro in a parallel flow condenser. A replacement original style compressor (4 Seasons) will be used and says it has the correct 134 compatible oil in it. Dryer is replaced. Soft lines replaced. Hard lines cleaned. The evaporator flushed as best I can while in its installed position. I found zero contamination in any part of the system.
Questions:
1) Assuming I got all the old oil out of the evaporator and other lines, dryer, and condenser will be new, how much more oil will be required?
2) How much 134 will be needed for an empty system assuming the parallel condenser is roughly the same capacity as the original condenser.
3) Will a small amount of unknown oil in the valve systems cause issue? Do they need to be cleaned/cleared of oil? Will the AC cleaning solvent cause issue with internals of the valves?
Thank you for assistance.

[Stocker]

A little info from my notes, from when my AC was converted to R134a a few years ago. Pretty much everything was done same as yours.

Stock system takes 60 oz R12 + 10 oz mineral oil. Those amounts (or at least the refrigerant) is reduced by 20% when converting to R134a.

So the correct amount of R134a is 48 oz. I'm not sure about the amount of PAG oil that's required. But you say your new compressor already has it so you should be good to go.

I hope this helps a bit, but don't take it to the bank. Verify against other sources. Others here should chime in with more / better info.

[howzzzit]

Stocker is correct. If the compressor came with the correct oil that is all you need. Make sure to blow out any solvent you may have used. A small amount of residual oil is normal and unavoidable.
When you button it up and get ready to charge the system do the following.
Use a vacuum pump and pull a deep vacuum through a manifold gauge set. You should be down to around 28 inches of vacuum after the pump runs for a while. You can't run it too long. As it pulls into a vacuum it is removing air and most importantly moisture. Moisture is the enemy of any refrigeration system. Valve off the manifold and see if the vacuum rises. If it does you have leaks. If it holds overnight you're good to charge. When charging make sure you slightly purge the line with refrigerant while hooking to charging port. That way you won't let any air in the system. Weigh in the refrigerant.

Here's a 12 to 134 chart
https://www.electronicshub.org/r-12-...version-chart/

[Bigdav160]

Proper procedure would be to drain all the oil from the new compressor and discard. I assume your 4 Season compressor is a Denso style. It needs about an ounce of oil. The evaporator, condenser, POA and drier? Another 5-6 ounces. Very likely the new parallel condenser holds more refrigerant and is more efficient so I wouldn't reduce the charge from factory recommendations.

[jeffahart]

I installed a new compressor about five or six years ago. Did the 134 conversion. I tried to be exact, but who knows, the air gets cold... really cold, and I live where it gets really hot! Follow the specified capacities and you'll be fine. Get a small scale to weigh the 134. Don't over think it.

j

[PbFut]

Follow up question:
Pulling vacuum yesterday yielded 30- a tick. I understand that is normal and correct. Closing valves and allowing the vacuum to sit with pump off over night was the plan. An hour later I return to find the gauge close to zero. The most common issue is obviously a leak somewhere. Which I will look for tomorrow. Another idea popped in my head. Yes I am overthinking as usual. I cleaned out the evaporator best I could but I wonder if there was residual cleaning fluid in the coils. That fluid would gas off under vacuum. Is that possible for it to do so enough to move the gauge that much?
What is the best procedure for tracking down leaks. Compressed air into system and use soapy fluid at the joints? Or is compressed air not recomended? I am reasonably confident the new compressor is good as it had pressure when I removed the temporary backer plate and installed the new flex lines.
I very much appreciate everyone's reply's.

[kaycee]

Having just done this I had the same thing happen I found a o-ring tore actually 2 of them. Allso rechecked all connections and make sure your schrader valves are in good shape my hoses and pump,condensor etc were all new. I allso rigged up a fitting to my air compress to blow back through and find leaks then did a vacum and all was good. Mine held for a couple days ,make sure your connections are tight from the gauge setup.

[jeffahart]

I would do as kaycee says with one caveat. If still leaks, partially charge system and get a sniffer, it could be your evap core.

j

[PbFut]

Ok. Good suggestions. I will report back results this weekend.

[68 C10 Driver]

If you have access to nitrogen, pressurize the system with that, do not use compressed air as that will introduce moisture into the dryer unit. If you do not have nitrogen, then charge with 134 and dye and use a sniffer and black light to look for leaks. Check all connection points and any original components that you are reusing. The condenser or evaporator may have leaks that the sniffer or dye should expose. I wouldn't dump the oil out of the compressor, it should be fine and if under warranty changing it out may void that compressor warranty.

I have a EPA Section 609 (motor vehicle air conditioning) certification, just so you know I am not just throwing out Google facts. In my experience most times a system will not hold vacuum is because an O-ring is damaged, old component is leaking (i.e. condenser has a pinhole due to rock damage), or the rubber lines were not changed when converting from R-12 to R-134A. R-134A molecules are significantly smaller and will permeate R-12 line sets.

[68 C10 Driver]

Just another note, when you get to that point you fix the leak and recharge the system, when you add your R-134 be aware that the capacity is unknown...meaning you do not know 100% what the capacity of your system is supposed to be for the new refrigerant. So going off the advice given earlier on estimating that, also use a thermometer while charging so you can see what the air temp is at the vent. For R-134, the vent temp should be approximately 40 - 50 degrees lower than ambient air. So if it is 110 degrees outside, don't expect the A/C to be putting out 38 degree air.

[PbFut]

OK Good progress right until I ran it into a wall, so to speak. Found the leak with little effort. I failed to do a final tighten on one connection. Easy fix.
Pulled a vacuum and let is sit overnight. All good this AM.
I pulled in 7 more oz of oil as the compressor came with 3.
Pulled vacuum for another hour.
Purging feeder line and started introducing 134.
Got the 1st can in with little issue.
Second can seemed slower but it went in.
Go to put 3rd can and the seal fails to clear in the can. Me or the can or the tool?
I bought extra can so not concerned.
Next can won't release eighter. Not sure if it’s me or cheap China tool.
I can't even get refrigerant at the valve.
I am already getting pretty cold air so I stop to regroup.
I feel like its a good time to remove the connectors at the ports just to be sure and think this whole thing over.
Pull off the two connection hoses and the low side port adaptor is leaking. I tightened the adaptor not the Schrader and it gets worse. Back the adaptor off and the leak seams to stop. I know I checked the valve in the port adaptor before I put the unit on and it did not leak during pressure and vacuum test. Not thinking all the way through, I go to remove the adaptor, not remembering part of the procedure was to remove the original Schrader valve in the POA housing. There went 16 oz of 134.
SO, now I get to figure out is it my inexperience with the Refrigerant can or the Tap tool is bad. And I need to figure out if the low side adaptor is bad or I over tightened. That seems unlikely as I did not gorilla torque when installing but anything is possible when you've never done something like this before.
I hate doing things for the first time and no experienced partner looking over my shoulder.