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“Per Part” PAG Needs?

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  • “Per Part” PAG Needs?

    I’ve been through the info. provided in the reference information sub-forum here and have been finding some info. through web searches.

    But, based on the varying numbers I’ve found, I’m still unsure.

    Can anyone provide any info. one the amount of PAG that should be added on a per part replacement basis?


    How much PAG should be added if say ... just the drier is replaced?

    How about if just the liquid line is replaced?

    The evaporator?

    Are there any generally accepted and safe numbers that can be applied or are these those “dump out the old and replace what you dump” situations?

    Thanks in advance for any information.

  • #2
    Unless you are totally flushed out, blown out and known empty with OE spec parts you add what is suggested for the total oil charge with specific type. All the rest is educated guessing on what you get out and what happened that you are doing anything at all to a system.

    Factor how it quit and when such as while it was working it blew out all at once guess at the mess it made. Part by part is harder things like driers, accumulators if applicable drill holes in the old one when warmed up count what you get out. Condensers for 134a mostly HE are not cooperative if a compressor failure still do accumulate the most oil IMO pretty hard to know the things are like filters with very small passages.

    IDK - system that hold say 8 ounces you measure what comes out of things and add two unless totally empty is or was a fair guess. Just adjust the math based on known capacity if empty some hold lots more or lots less total. Way, way too much performance totally impaired up to choking compressors on oil starts another disaster.

    You can know it's over oiled if pressures and performance are erratic is a problem so is too little may have a noisy compressor that is NOT going to last if so. Each situation an educated guess unless you begin all over from known empty is about the best I can say and probably what you'll find searching around,
    MetroWest, Boston


    • #3
      I agree with Tom. The real problem is: you don't know what has happened in the past, how many times it has lost refrigerant (and therefore some oil) and been "boosted" back to working with just refrigerant and no oil. I've always felt it better to be SLIGHTLY over on oil then low on oil. If you go way over, you can slug the compressor, but you'll likely see erratic pressures long before, as the excess oil passes through the metering device. Too much will reduce heat transfer and degrade performance
      Too little, and it doesn't take a big reduction in oil, and the compressor will fail. Gone are the days of large compressor sumps. My A-6 calls for 10 oz, most of which stays in the sump to be pumped by the compressors oil pump. The big recips like the York and Chry RV-2 also had big oil sumps. Todays little compressors store very little if any excess oil and don't fair well if starved for oil.