I recently replaced my A/C compressor, expansion valve, drier,and the high low pressure switch, and aux fan temp switch. I removed the condensor and flushed it repeatedly with A/C flush, then blew it out with compressed air, then flushed and blew out the evaporator and the line from the evap to the compressor,.....blew those lines out from inside the car while the expansion valve was removed. And flushed and blew out the line up front with the muffler cannister on it. I didnt have time to complete the installation, so the system ended up being open for a few days to a week. I installed the new compressor, then the expansion valve using new green O-rings, (previously added the recommended 5.5 oz of compressor oil, then an additional 5 oz of oil divided between the not yet installed drier and the condensor (actually did this before re-installing it). I couldnt find any information on how much oil to ad to the system, I was directed to a web page somehwere that stated the A6 rotary compressor should have 5.5 oz, and then from there I just got drips and drabs of suggestions on total system capacity of 9-11 oz of oil. I never new for sure if any of it was correct. The freon requirement is 2.9 lbs of R12 or 46 OZ. I installed either 2 cans or 2.5, cant recall, they were 12 oz cans and I was just guesstimating as I was not using a scale (can a scale be used with the small cans?)

With the new drier in place, I vacuumed to -30 and let it run for an hour and a half or so. Charged with R134a and found on a 100 degree day I had 45 psi on the low side, 320 on the high side, and about 70 degrees at the center vent when driving.

The clutch on the (reman) compressor gave up after a few hundred miles last week,...............so, I have the system apart again, drained the oil from the compressor to measure it.

HERE ARE MY QUESTIONS:

1-When I drained the compressor oil it came out like bubbly champagne,....it took about 10-20 minutes for all the bubbling to subside--IS THIS NORMAL?

2- The PAG150 is fairly dark now, it was clear when I installed it, IS THIS NORMAL?

3-Im seeing something that I am pretty sure is a small quantity of water in the drain pan,...under the oil,...........I'm thinking this is NOT good......AND IT OCCURS TO ME THAT I USED COMPRESSED AIR WITHOUT A DRIER IN THE LINE TO BLOW THE SYSTEM FLUSH OUT,...IT WAS ALSO RAINING ON THE DAY THAT I INSTALLED THE DRIER, AND I REMEMBER SEEING SOME WATER DROPLETS SPATTERING IN THE AREA OF THE NEW DRIER AND THE OPEN A/C LINES,....THINKING THAT SOME MAY HAVE SPATTERED INTO THE OPEN LINES, OR THAT 100% HUMIDITY MAY HAVE COMPROMISED THE INSTALLATION.

I pick up my replacement compressor this morning, but will wait for thoughts on this before proceeding.

4-A fried has said that he has often poured out whatever is in the drier and added fresh oil of a like amount and never failed to have a system work after a vacuum and re-fill.....thoughts on this?

To begin with, you said you charged it? I assume this is an R12 system converted to R134a. If so, what percentage of the R12 refrigerant weight did you charge with R134a.

Secondly, blowing out the lines with compressed air, then letting them set, made for a VERY contaminated system. Even with a fresh r/d, I would be concerned about it. It would be better to sweep the system with nitrogen or some other inert gas. In the old days, we swept them with a short blast of refrigerant, but that is illegal today.

PAG is not the best oil for a converted system.

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Yes, converted from R12 to R134a. and, now the system is open again because My part supplier did not have another compressor, wont have it until later today.

I have access to a bottle of Nitrogen, How do I Sweep the system, and then assuming that doing this will displace compressor oil, how do I compensate.

The Harrison/Delco rotary compressor that the 126 uses requires a comprssor oil with viscosity 150. I had planned on using the BC universal synthetic lubricant, then found it was recommended only up to viscosity 100. That left me with PAG 150 (AFAIK),....Im open to alternatives.

should I tear the system completely apart again and flush again then use the Nirtogen to purge,.....or could I use your sweeping procedure with everything still hooked up (accept for where I disconnect to purge with the nitrogen.

No the sweeping will only be used to REMOVE the flushing agent. After such a compressor failure, you need to break every connection and flush EVERYTHING thoroughly. Use the nitrogen to blow out the flushing agent from each component. It wouldn't hurt to install a suction side filter just before the compressor inlet after a couple of compressor failures.

You are basically starting all over again with this compressor and it could be that there was debris in the system that took out the recent replacement. In this situation, it wouldn't hurt to use a clean white cloth over the outgoing end of a component as you flush it to trap any debris just so you can tell when that component has been flushed clean.

It's been a long time since I messed with an R4 on anything, so I don't know about the oil.

When it's back together charge by refrigerant weight, not pressure. Start with 60% of the specified R12 weight in 134. See how it cools and how the pressures look and go up in SMALL increments after that. I have had converted systems work well with as little as 60%. The less you can get by the less strain on the compressor and the better cooling.

Now, I can't help but ask this: If you are going to go through all this work, which is the same work it would take to reverse convert to R12, why would you not just go back to R12?

Edit: I forgot to respond to your item 4 in the first post. If you mean that he is proposing that you simply replace the r/d and the amount of oil taken away with it, then I say in the case of a catastrophic compressor failure, your willingness to do this will be directly related to how much you enjoy going through this entire flush, r/d/TXV/Compressor replacement process. You indicate that you are replacing due to a failed clutch, but that COULD be an indication of a failing compressor. You could have been overcharged that compounded the problem.

Drastic situations, call for drastic action. If it were mine, I would break all connections and flush until the cows came home and try to get a suction side filter in place. I would then double check oil qty. because I had in my mind that this system takes 8 ounces of oil, but I am NOT sure, so don't believe what I say, just double check. I would then replace the r/d for sure, and bolt it up very last thing with the vac pump at the ready to start evacuating as soon as the r/d is in place.



Hope this helps

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Larry, the original (A6) compressor didnt fail,....but it was making an odd and somewhat loud Whirring sound. It may have been overcharged long ago,.....the car was in storage for 10 years after it was stolen from me in 2000 or 2001. I finally decided it was time to fix everything wrong, and sell it. So, thats the only reason I have done this. New tires, brake calipers, hoses, pads, master cylinder, Upholstery repaired and refinished as needed. New CD player, and some other odds and ends. I replaced the windshield and console wood with new just before it was stolen and subsequently put into storage.

I wanted to convert it to R134 to make it more consumer appealing. Guess that plan blew up.

Now I have a system that has had both R12, and R 134a (and Envirosafe Hydrocarbon refrigerant) and related oils in it. I just read this morning in the Mercedes technical companion that this is a no-no as the residual mineral oil in the hoses will contaminate the system when adding the PAG.

I just about out of money for this project (lost my job, was trying to create a good product and some cash flow)

I now want to proceed as quickly and cheaply as possible to getting this system reliable and cold.

Do I pull the condensor and the expansion valve and drier out again? Replace the drier and expansion valve again?

I dont seen any metal in the oil I drained out of the compressor (about 4 ounces)

Well, that sheds a whole new light on the project. I've been in such situations, so I know how it can be.

I'm worried about that oil though. In your current situation do you have TIME to put into it? Probably a silly question since you're out of work, but when I've been out of work in the past, I was hustling so much trying to do other things to make ends meet that I didn't have a lot of time.

If you have a lot of TIME to put in it, but limited funds, I will think through it and see if we can come up with something.

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Larry, I appreciate the offer, I can relate to a constant scramble to make ends meet. I drove a hotel van during Austin SXSW music festival, I am studying to get my CDL in case nothing else develops, have sent out and hand delivered countless resumes. Waiting to hear on a follow up interview with State Farm as an Auto damage adjuster, figured it would be a good way to use my knowledge of car repair.

But, I am commited to getting this car right and selling it. Its been in storage and now my driveway for far too long,.....Its time to pass the batton on to a new owner. I also have an 83 SL I am putting new upholstery and wood in to.,....then its for sale as well.

I picked up the bottle of nitrogen from my friend tonight, I have a gallon of A/C flush coming tomorrow with a new compressor, drier, evaporator, orings etc for my truck (the clutch gave up on it's compressor 2 weeks ago,......original comprssor, never a system recharge..........241,000 miles. Always blew ice cubes.

I am going to O'Reilly's tomorrow to see if they will unwind my purchase of their re-man compressor, if they will refund me my $175, I can buy a NEW S6 (an A6 with mechanically updated, more reliable guts and clutch,....the common failure point).....it $425 with a new drier, expansion valve, orings, flush and oil. (complete install kit---carries a year warranty)

I'll consider R12, or anything else,....just as long as it works.

Are you in or near Austin?

To start with, did you troubleshoot to the point that you know that the problem was the clutch itself?

When you turn the old compressor at the very front, rather than at the pulleys, does it turn smoothly or feel like it's full of rocks?

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unfortunately, I didnt think to test the compressor to see if it turned freely,......I gave it to OReilly a couple of days ago. Probably gone now.

There is something wierd going on with the oil I drained out. I have the 4 oz of oil from the compressor in a glass measuing cup. There are two distinct layers, the top layer is about 1/4 inch thick and maybe a light amber color,....nearly clear with the amber color. the layer below that is about 1.5 inches and is nearly black. If I pour the oil into a silver pan,...then it really looks odd,......almost like water and oil not mixing,....but appears to be two differnt oils, that wont mix together....suggesting that either I didnt get all the original Mineral oil out of the system when I flushed,....or,...Mineral oil was imbedded in the old hoses, and it contaminated the new PAG oil.

I'm in Cedar Park, about 20 miles northwest of dowtown austin.

I think you didn't get it all flushed. It is difficult to get the evapororator and condensor flushed thoroughly. Did you break EVERY, SINGLE connection? How did you flush? Did you use a pressurized flushing vessel with a rubber tipped blow gun, or did you just try to blow some Brake Kleen through?

You need to find a way to seal off and FORCE solvent through each component, especially evaporator and condensor and then blow the solvent out THOROUGHLY. You really need to replace the receiver/drier because yours is most certainly saturated and this oil mix is inside of it. Remove the TXV and make SURE that it is clean and clear.

This will be a lot of work to thoroughly flush, but with it flushed and ALL the solvent blown out, you will then have a good starting point. If you were keeping this car it would really be worthwhile to go back to R12, but I THINK if you get the correct amount of Ester in the system and start with a couple of cans of 134, then go up in small increments, you can make it cool.

During the flushing process, seal off each component after it has been flushed clean and the solvent blown out with nitrogen. Once the compressor is bolted up and all components are flushed, begin connecting things up and keeping the end opposite where you are connecting sealed until you are ready to connect that component.

Put the r/d in place last thing and immediately start the vacuum pump. This all MIGHT be overkill but after all the moisture you described and the oil mix you found, I think it is justified. If you find any grey powder in any component, then you need each component blown clear until no residue is flushed through a white cloth.

I don't know what to tell you about the 150 viscosity recommendation except if it were mine I would just use Ester if going back with 134. Also using Ester in a THOROUGHLY flushed system, you have the option to later simply recover the 134 and charge with R12.

You are probably right on the 5.5 oz., but do some research and ensure that is the correct amount. Distribute the oil throughout the system as you are putting it together, a couple ounces in the condensor, a couple in the evaporator and some in the compressor to add up to the total amount.

Once the system is thoroughly evacuated, start with two cans of 134 and then add a little from a third can and see where you're at. Charge in small increments after that while monitoring the vent temperature. Use a high flow fan in front of the condensor if possible and run the idle at about 1500 RPM.

If you have any questions post them here or feel free to PM me. There are lots of a/c savvy people on this forum who are happy to help. They all have different ideas about refrigerant, but many of them understand a/c.

Hope this helps. Best of luck. I will try to check the forum a few times during the weekend.

One other thing. There are more a/c guru's that post in the Diesel Discussion forum than on this forum. In fact one of the moderators, VSTech, is a professional HVAC guy and is EXTREMELY knowledgable and helpful.

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2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution