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**mael**

I'm a learner on car a/c systems, but I'm a fast learner.

My neighbour hacked-off a compressor of a scrapped car to get parts to repair the one in a similar car he's trying to get done.

The original problem was the outer-most plate. The flexible connection between the inner rim and the outer disk was rooted, so he figured he'd just use a part from another a/c from the same type of car.

Unfortunately the compressor is wildly different, and the part won't fit.

I should add that my neighbour is a real grot and he loses parts willy nilly, and also leaves things like a/c compressors outside in the weather until he either finds a use for it or (more usually) it gets so stuffed-up it is unuseable and someone kindly tidies up his trash.

I've completely disassembled the compressor he hacked-off for the outer-most disk, and I've cleaned all the parts and reassembled it.

My question concerns the oil. There was a bit of oil in the old compressor, and I don't know what type it was. Obviously I need to add oil to my (now sparklingly clean) compressor before trying to run it and charge it.

The working gas is R134a. Can I use some regular motor oil? Or does it need to be a special oil? If there's a good chance I can get away with slipping engine oil in the compressor then I'd like to take the chance.

How much to put in is also a mystery to me, but from a few clues I think I can guess reasonably accurately. The car is a 660cc Suzuki Kei. I think the amount of oil it'd need is well below 50cc, and probably between 25 and 35cc.

Would someone kindly advise?

**CourtDude** · (This post was last modified: 10-24-2012 02:52 PM by CourtDude.)

Good luck on your A/C project!!! Two minutes of Googling got me this answer -

LUBRICANTS - POLYOL ESTERS (POE's)

A. Miscibility

1. Miscibility is the ability of the lubricant and the
refrigerant to mix. This miscibility is a very
important factor in the returning of the
lubricant to the compressor in a refrigeration
system over its range of operating
temperatures.

2. R134a and mineral oils are not miscible.

3. Polyol ester oils and R134a are miscible. The
miscibility of polyol ester (POE) oils and
R134a is similar to that of current refrigerant
oils and R22.
Some types of POE's are fully miscible with
R134a (as are synthetic alkylate and R22),
while some POE's are partially miscible with
R134a (as are mineral oils and R22).

B. Moisture

1. Polyol ester oils, while not as hygroscopic
(ability to absorb moisture) as earlier
considered PAG's (poly alkylene glycols), are
100 times more hygroscopic than mineral oils.
This moisture is difficult to remove even with
heat and vacuum.

2. Utmost care must be taken to prevent
moisture from getting into the refrigeration
system. Do not leave the compressor or
system open to the atmosphere for longer
than 15 minutes maximum. The preferred
method of assembly would be to remove
system component plugs and caps just prior to
brazing. The maximum system moisture
content after completing system processing
should be 80 PPM. After running the system
with the appropriate drier installed, the system
moisture level should be 10 PPM or less.

3. Always use an appropriate drier in the system
when using R134a. (See section on DRIERS.)

C. Compatibility

While polyol ester oils are compatible with
mineral oils, they should not be
indiscriminately mixed with mineral oils in
R134a refrigerant systems. This practice could
result in the inability of the oil to return to the
compressor and/or reduce heat transfer
performance in the evaporator. However,
small amounts, up to 1% of mineral oil are
acceptable in field retrofit situations.

**mudma**

You should be carefull playing with aircon,i used to work with office sized ac units,my boss said the oil in the compressor can turn into a substance v.close to mustard gas,i dont know what can cause this or if it can happen to automobile ac units because if eiffernt refrigerants but I would reasearch it a bit first,i remember gettin sum on my hands once and I stupidly.had a cigarette,burnt the shit out of my lip lol

**LoP Guest** lop guest User ID: 129215 10-24-2012 03:04 PM

It's not as easy as taking it apart and cleaning it.
There are seals, o-rings and maybe reed valves all of which must be carefully examined, serviced or replaced.

If you open the system you need to replace the dryer. You should also replace the expansion valve.
Call the dealer and ask for the part number on the oil. Look it up it is probably POE oil. The amount you need in the entire system should be on a sticker under the hood, this will also tell you the amount and type of refrigerant to charge by weight.

You must pull a vacumm on the system before charging.

**mael**

mudma Wrote:

You should be carefull playing with aircon,i used to work with office sized ac units,my boss said the oil in the compressor can turn into a substance v.close to mustard gas,i dont know what can cause this or if it can happen to automobile ac units because if eiffernt refrigerants but I would reasearch it a bit first,i remember gettin sum on my hands once and I stupidly.had a cigarette,burnt the shit out of my lip lol

I'm far from an expert, but I think a dangerous substance can be formed with the oil/working gas in a R12 system.

This is 134a, so there's no danger of creating anything like mustard-gas.

* Gawd knows if engine oil and 134a makes a mess though!

**CourtDude**

mael Wrote:

mudma Wrote:
You should be carefull playing with aircon,i used to work with office sized ac units,my boss said the oil in the compressor can turn into a substance v.close to mustard gas,i dont know what can cause this or if it can happen to automobile ac units because if eiffernt refrigerants but I would reasearch it a bit first,i remember gettin sum on my hands once and I stupidly.had a cigarette,burnt the shit out of my lip lol

I'm far from an expert, but I think a dangerous substance can be formed with the oil/working gas in a R12 system.

This is 134a, so there's no danger of creating anything like mustard-gas.

* Gawd knows if engine oil and 134a makes a mess though!

See my post above; they are NOT compatible!

**LoP Guest** lop guest User ID: 129215 10-24-2012 03:20 PM

Motor oil cannot be used in an ac compressor.

**mael**

LoP Guest Wrote:

It's not as easy as taking it apart and cleaning it.
There are seals, o-rings and maybe reed valves all of which must be carefully examined, serviced or replaced.

If you open the system you need to replace the dryer. You should also replace the expansion valve.
Call the dealer and ask for the part number on the oil. Look it up it is probably POE oil. The amount you need in the entire system should be on a sticker under the hood, this will also tell you the amount and type of refrigerant to charge by weight.

You must pull a vacumm on the system before charging.

Taking it apart and cleaning it was a necessary step because it had been sitting outside for three months, and of course it was corroded inside and half-full of water and the remains of the oil.

The a/c system is not drastically exposed to the elements. After removing the lines from the compressor during removal I plugged the ends. The actual compressor, of course has been fully exposed to the air. Thus, I don't think I'm, going to be replacing any drying medium... though I appreciate I should, and I might end up having to advise my neighbour that it is essential.

I have something that can pull a relative vacuum - from a hospital actually - used to suck the sputum from people, I think. That can be tweaked. I've also got an old fridge compressor which I can use to pull a relative vacuum if the hospital equipment is too weak.

No reed valves. There is a pressure sensor on the casing, and that's about it as far as electrics are concerned apart from the magnetic clutch.

'O' rings? Hmmm! Well if it leaks then at least I know how to get it all back together again quickly.

I'm still not clear on which oil to use. Engine oil? Compressor (domestic) oil? Brake oil? Baby oil? Oil made from boiling human flesh?

**mael**

See my post above; they are NOT compatible!
[/quote]

OK!

**mael**

LoP Guest Wrote:

Motor oil cannot be used in an ac compressor.

So I'll be flushing the bit I shoved in there out with brake-cleaner.

I used a bit of WD40 during reassembly, and I put a smidgin of engine oil in it to get the bits rolling.

* Clean it out somewhat, and then put what in it? Mineral oil? Brake oil?

**mudma**

I worked at a printing press too,they.used shell gear oil in the machine compressors,but dont use that coz of the way ac oil mixes.with refrigerant,try searching car mechanic forums,sumone must have rebuilt a modern car ac unit

**LoP Guest** lop guest User ID: 126194 10-24-2012 03:28 PM

The oil is IN the refrigerant.

**LoP Guest** lop guest User ID: 9894 10-24-2012 03:31 PM

they sell cans of oil charge at the autozone

**mudma**

You will want a gauge to see what vacuum you are pulling,we did it to check for leaks in big units,vacuum system and see if it holds vacuum for half hr,if all good gas it up to pressure.

**mael**

LoP Guest Wrote:

The oil is IN the refrigerant.

Is it? That'd be awfully convenient if it is.

So that being the case I can advise my neighbour to buy a couple of bottles of 134a from our local have-everything shop, charge it to the right pressure, and the job may be done?

On my searches, the issue of compressor oil and the working gas are two separate subjects, so I thought they were different jobs. I thought you load the gas in the low pressure line, and the oil goes directly in the compressor AFTER the system has been purged of 134a.