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Wednesday, June 19, 2013

A/C question on whether to add some PAG oil or not?

I don't think the make/model is important, but we have a 1998 Mazda
Protege that we just love. I went to recharge the R134A refrigerant in my air conditioning system (I
don't think it ever had a top-up since it was manufactured) but I
forgot to purge the line from the kit I bought. I got air into the
system and it's running strange. If I had done it right I would not
have had any issues, I'm certain.

I tried bleeding some of it off then adding some a few times, and it
didn't get any better. A licensed A/C professional (he installed my
home A/C and heating system) said that air can make the compressor
cycle on and off and when it's on it can pull very hard on the engine
when the air gets to certain parts of the system. So I decided to
remove the R134A and the air and start over.

I am not going to remove the compressor to drain and measure the oil
removed from it. If you knew how cramped the area is where the
compressor is located you would understand why.

I now have an evacuation pump that will pull a vacuum down to 75
microns (at sea level, I guess), and a set of gauges. I am familiar
with the refrigeration cycle and process, and have viewed some decent,
well-explained YouTube videos on how to evacuate the system and
recharge it.

As far as I know, we have no leaks. I should know for sure after I see
that the vacuum holds for 1/2 to 1 hour after I shut the valves and
remove the pump.

Assuming that I don't have any leaks, I want to know if I should add
any PAG oil to the system or not. I've read that the oil will
evaporate under vacuum. I've also read that the oil will stay in the
compressor and lines.

I bought a 3 oz can of PAG oil that gets added through the gauge set
in case I need it. The under hood sticker does not tell how much oil
to use, just the amount of refrigerant.

Can I safely assume that the oil is still in the system or should I
add some? Too much oil can be detrimental to the system.

I guess what I really need to know from someone more experienced is if
the oil evaporates with the refrigerant and any moisture in the system
(there shouldn't be any moisture in my system) when a vacuum is pulled
for 1/2 hour or so.

If someone here knows whether I should add the 3 oz can and assume
it's not too much or if I should avoid adding any since I haven't
opened the system nor am I aware of any leak, please let me know.

I don't need to know about the general procedure, how to use the
reclaimer, etc., just some information about the oil. However, I'm
open to any tips you might have.

1 comment:



  1. Under the hood is a sticker that specifies the amount and type of refrigerant usually around 24oz on a small car. Rule of thumb is for even 12 oz of refrigerant use 2 oz of oil and don't worry about what may be remaining in the system. Evacuate the system to at least -19, ad a can of oil the a can of refrigerant. HOWEVER, you CAN get it in an ALL-IN-One too, Sealer, Oil and Refrigerant, which I prefer. Pressure on the low side should run near 30 psi when running. You may wish to change your Dryer at the same time.

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