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Old 07-04-2002, 07:16 AM
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AC 134A retrofit kit

The 134a retrofit kit says to remove the old compressor oil , how can that be done? I have a '83 300d, thanks.
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Old 07-04-2002, 07:20 AM
engatwork's Avatar
Join Date: May 2000
Location: Soperton, Ga. USA
Posts: 11,878
Those kits leave a lot to be desired. The only way to remove everything is to pull a vacuum on the system then refill/charge. I always replace the dryer whenever my a/c is opened up for any reason. I will warn you - you will probably not be impressed with the performance of the a/c in the W123 when running 134a.
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Old 07-04-2002, 07:53 AM
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Join Date: Sep 2001
Location: Houston, Texas
Posts: 1,071
To remove the old oil, one must flush the system with a solvent cleaner solution. That means removing the expansion valve. Its requires that all components of the system be flushed untill all the oil is removed. Not an easy task. Simply evacuating the syetm does not remove the oil. It only removes the freon and any other gasses that are in the system.
I got too many cars!! Insurance eats me alive. Dave

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Old 07-04-2002, 09:31 AM
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dpetryk is right. And since you have everything apart for flushing, replace all o-rings with r134 type using Nylog lubricant, replace filter -drier with correct type, replace pressure switches, and H block with r134 types.

I'm not sure which kit you are referring to. There are kits that have adapters, the correct o-rings and oil. That is part of what you need. Other kits from Wal-Mart etc are simply a hose a few cans of R134 and an oil charge of some sort. These kits are called "death kits" by many. They don't kill you, they just kill your A/C system.

I suggest that you stay with R12 or if you insist on converting, do it right or you will be sorry in the long run. The cost of R12 is coming back down making R12 an even better choice.

Good luck,
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Old 07-04-2002, 12:06 PM
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Join Date: May 2000
Location: Soperton, Ga. USA
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Thanks for the correction ya'll .
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Old 07-04-2002, 12:16 PM
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Join Date: Jul 2001
Posts: 613
The retro R134a kits list the oil as being compatible with the R12 oil. I replaced most of my lines, condenser, AC filter, Evaporator, expansion valve, o-rings and a ac filter switch (that was leaking).

Charged the system up to about 30 psi of 134a, which is about 80%, added a can of Maxi Cool and with the recirc on, the air is blowing about 48 degrees. With the recirc off, it blows about 55 degrees.

No problems and everything is good. BTW, I watched my local MB dealer quote a guy $500 to convert his system then proceeded to watch MB evac the R12, change the AC filter, a couple of o-rings, install some high/low side adapters then charge the system up with R134a from a large tank. All for $500.

Guess MB does not feel the need to do anymore when converting from R12 to R134A.
1993 500E
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Old 07-05-2002, 10:55 AM
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Join Date: Dec 2001
Posts: 571
I agree with Larry. Get yourself a 609 certification and stay with R-12.

It's my belief that systems that come from the factory with R134a work fine for the most part. Some retrofits work; many do not. In order for a retro to work and I mean work for the long term, a long list of tasks must be performed correctly. Even when this takes place, people are often disappointed in the results.

Steve Brotherton had an interesting comment about R-12 not so long ago. It's the cheapest component in the system, yet people are in awe that they have to spend a few bucks to keep cooling with it.
If your system is leaking, find the leak and fix it. You can convert to R-134a, but you're still going to leak.

My 2 cents.
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Old 07-05-2002, 12:26 PM
Join Date: Mar 2000
Location: Gainesville FL
Posts: 6,844
Just a couple points on the discussion.

We have easily converted a thousand cars of numerous brands. We still do it because that is where the market went. We started doing conversions the first year R12 got taxed. In the beginning there were all kinds of horror stories due to potenial mixtures that would cause all kinds of problems. One concept was that the two oils would make a foam that would harden sort of like the stuff you squirt in walls that turns to styrofoam.

It turns out that the worse thing that seems to happen is poor air conditioning, maybe a few extra leaks. It is now thought that the mineral oil from the R12 system just moves around the system taking up space. It pools it the least turbulent areas and really does nothing. This is now the position of MACS ( the Mobile Air Conditioning Society). They are one of the testing services that register R12 handlers.

The other point has to do with evacuating systems, the concept has been resolved that evacuation only pulls gases from the system. Think about trying to suck the Coke out of a Coke Bottle vertically (without a straw). Won't happen, BUT, if you heat the coke and let it boil then one can easily suck off the steam. The boiling point of water is 212deg F at sea level. High in the mountains water boils at less than 200. In space, water boils at room temp (one of the reasons for pressuring space suits).

The point of evacuation is to take the system to outer space conditions and suck off the gasses this causes. This is mostly water that disolves in the A/C oil but also can be the liquid remains of arromatic flushes.

As it turns out, standard gauges are inadaquate to verify the level of vacuum that is appropriate. AND unless the vacuum pump is regularly maintained with regular changes of oil, the best of pumps will only go low enough on very hot days. Just sucking on it guarantees nothing.
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Last edited by stevebfl; 07-05-2002 at 12:32 PM.
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