Thread: A/C Experts? Compressor replacement...

Car in reference is my '93.5 G20 running R134a from the factory. I've read "Project A/C to beat the heat" several times but I'm concerned with the amount of oil that may currently be in my system.

Last year the pulley bearing went South on my A/C compressor so I bought a "rebuilt" unit and had my friendly neighborhood mechanic do the install. The POS rebuild, which actually appeared to be a part someone pulled from the junk yard and repainted, lasted a total of 48 hours before it was leaking PAG oil from behind the pulley. I then put the bypass belt on and said f#@k it, but I eventually picked up a good quality rebuild and new receiver/dryer.

If I understand correctly, little oil circulates through the system and most of it ends up in the receiver/dryer when the system isn't running so a good portion of it may be sitting in there, and also in the broke-ass compressor, at least what didn't already leak out. Is that true, or could there be a good portion of oil trapped in the system somewhere else?

The new compressor came with PAG oil in it and from what I understand, typically the amount of oil in the new compressor is enough for the system it's intended for, BUT my concern is that I'll have too much not knowing if there is some hiding somewhere.

Any tips and/or advice would be greatly appreciated. I may tackle it this coming weekend or the following. Thanks!

Unfortunately, my suggestion is to spend the money to have it done right. Most likely the system is dirty and NEEDS to be flushed or your new compressor won't last that long either!

I installed a complete AC system in my NX using some used parts. However, I had the compressor rebuilt and the lines modified for R134a fittings, replaced all orings, bought a new drier but used the old condensor. It failed 3hrs into the 22hr drive to last year's convention. The failure was due to the years of debris that had built up in the condensor, even though I meticulously cleaned it and straightened fins prior to install. There was enough restriction in the condensor that it couldn't do it's cooling job properly...and since temp/pressure are directly proportional, the system eventually built up too much pressure and blew out the overpressure switch on the compressor (which my mechanic had a hard time finding). I did all the labor and just had him do the flush and charging...I don't recall what I paid so it wasn't enough to really stand out in my memory but I'll check my records when I get home - I'm guessing a couple hundred. Well worth it to know it's done right! It's been going strong ever since and will be going strong for this year's 22hr drive!

IMO, the AC system is not an area you should enter unless you absolutely know what your doing. You'll just end up spending more money in the long run and will eventually concede to paying an 'expert'.

Before (and even after) the bearing issue with the factory A/C it blew nice and cold with no issues, but I replaced it because I didn't want it seizing up unexpectedly and snapping the belt. After the "rebuild" was installed last year it worked fine for a couple days before leaking PAG from the shaft seal, at which point I swapped in the bypass belt and left it go.

While I can't be certain I doubt the system is contaminated, but since everything is bought and paid for already I'm going for it, too late to turn back now. IF this doesn't work out I'm absolutely 100% done with it, but I have to give this a shot.

Said the stubborn Dutchman...

@1fastser, based on what you said above I think I'll add this to my itinerary... Interdynamics Professional-Grade Aerosol Power Clean and Flush (17 oz.) CA-1: Advance Auto Parts

I hadn't even thought about flushing it, but for another $17 it would seem to be a good idea.

@bhowle

According to the FSM the compressor oil capacity is 6.8-7.0 oz., which is also the total capacity of the system, so if there's 7 oz in the compressor I should be good.

Where did you get your compressor from?

The first one was a joke. Seriously looked like someone simply pulled it from a yard, painted it and shipped it... rycompressors1 on eBay Didn't have but a couple of negatives at the time, but look now.

The one waiting to go in form these folks... bigfoot0492 on eBay

Yeah I know, "eBay", but we're beyond that at this point...

The oil capacity listed in the FSM for the compressor is for a factory new compressor. The replacement compressors came with enough oil for the entire system.
This is a throwback to the days of ac being added on after factory build of the car.
The oil will end up spread throughout the ac system.
The drill for compressor replacement is:
Drain and measure oil from original compressor.
Drain oil from replacement compressor, and replace with amount same as from original compressor.

Too much oil in the system will result in very poor cooling.