Thinking of buying a new a/c compressor "kit" - Page 3 - PeachParts Mercedes-Benz Forum

showme · #1 06-19-2010, 11:21 PM

There you go. Thanks for more information that I would have had no idea about, on both fronts. The compressor info I can use, and had no idea. And I guess I've either never read about the problem writers, or it went over my head. Sorry if it sounded like I was on a soap box. Thanks for the extra compressor input, though.

Cr from Texas · #2 06-20-2010, 11:20 AM

Quote:

Originally Posted by leathermang

Showme,

The fact is that our compressors are the old style which has NO OIL SUMP..
This makes them more dependent on the proper oil being used because the only lube they get is what is circulated through the system..
So , OIL MISCIBILITY , the ability of the oil to be dissolved in the refrigerant so it can be carried around and around the system.... is MORE important on our systems with the Delco R4 than it is on later swashplate type compressors...
Cr, that is great that you used what I have been preaching ( and is approved by the EPA as a test method which allows the venting of that test load ). I am trying to figure out how to divide my 15 oz can of R22 evenly without an accurate scale.
I believe that people can pretty much do whatever they want with THEIR cars... although I do promote following the EPA rules... but when it comes to promoting junk procedures or junk refrigerants or lazy methods... I believe the people on the forum not yet familiar with what is safe and long lasting need to be warned...
If Larry's post was a rant... it had ten years of provocation by some real gems of trollers and bad physics promoters behind it....

Since I caught the new compressor leak before loosing the R12, it was not necessary to replace the drier and flush. However, I don't know how much oil I lost with the leak. I added more oil with the second compressor but I only hope I have the right amount in circulation. I'm trying to figure out a method to sample what's in circulation and determine the oil concentration - should be doable.

Leathermang is another of those type #3 posters that I read carefully. Maybe I can payback with the R22 issue. I didn't have a can of R22. I drove to my favorite AC tech that services my home R22 unit. He added (by weight) the 2 oz of R22 (didn't even charge me), then I drove home and added the nitrogen.

Cr from Texas · #3 06-21-2010, 10:16 AM

The leak was at the compressor and I found the leak before loosing R12 due to oil spots on the driveway. I assume the R12 was pushing oil out a leak at the low point in the system when parked. I assumed a 2 oz loss.

If I had thought to plumb in a valved test loop in one of the lines, I could capture a measured sample and determine oil content by GC in my lab. Problem now is getting a precise volume sample.

There was an oil analysis device on ebay that you screw into the Schrader fitting. I couldn't come up with a reasonable explanation of how that could work so I didn't order one.

leathermang · #4 06-21-2010, 04:19 PM

CR, You are probably in great shape..

but for the record.... on places like Aircondition.com where professionals talk amongst themselves... they usually consider any leak as a contaminated system which needs to be flushed and have new R-Dryer installed..
This is counter intuitive to the layman since it seems like there is pressure all over the system all the time...only varying more when the compressor combined with the TXvalve cause more differential... so a small leak would only mean stuff was being pushed out..
But as a dynamic system when running.. that is not necessarily the case...
So if some has a leak and wants to be safe... then treating it like it has moisture in it is the safest thing to do.

JHZR2 · #5 06-22-2010, 07:45 AM

Just my update - got my kit (new comp, R/D, EV) from Phil, and it was all installed by last Friday. Picked the car up yesterday, in severe heat - 95 degrees or so on the roads. R12 system took a second to start cooling, but then blew frosty air for me. Nice and cold...

leathermang · #6 06-22-2010, 08:27 AM

If your reputation is on the line for future work...
then the decision to treat any leak as needing a fail safe slam dunk service procedure may well be worth the cost.

When spray painting cars in the past I always had a pressure gauge as close to the paint can as possible... well, close and easy to live with.. this meant on my belt loop for me.. because the pressure specified by the instructions talked about actual pressure at the spray can... so I had my water filter and pressure gauge on my belt 3 feet from the sprayer... it is amazing how much drop in pressure shown at the compressor exists at the time the paint trigger is pulled ( not talking about HVLP systems here) at the point of spraying.... the friction inside the air hose causes a real drop in pressure for an instant when the trigger is pulled....
I see this as the in the same type of situation in the AC system... if you have a clutched compressor like the R4... when it starts up each time... all that has to exist in the AC system is that the friction or availability of refrigerant between the TXvalve and the compressor is enough that the pressure drops significantly... and could in fact be enough to draw air and moisture into a leak in some situations...
Given the cost of fixing a system which refrigerant and oil have combined for long enough to cause acid to eat out some inside part of a metal line and then those particles get carried to some bottleneck to cause serious problems like NO COOLING in Texas heat... a life threatening deal sometimes... I can see a cost/risk analysis which would favor being perhaps overly safe technically in order not to get caught short later on and away from the means to address the situation ' at one's leisure' ...

Graham · #7 06-24-2010, 10:36 AM

Just another piece of information re the hydrocarbon based refrigerants.

I have an '85 300D that was converted to R134a when the original R-12 compressor failed. The replacement compressor failed the next year. It was replaced under warranty with a rebuilt and that unit lasted for about 4 years. It eventually seized and I gave up on A/C because we no longer used that car for long trips.

But, my wife drives the car and has been complaining about lack of A/C. So, I took it into a local A/C expert. This is the best A/C shop in our area and even the MB dealer uses them. They SUGGESTED I switch to a hydrocarbon based refrigerant. I asked why and they gave several reasons. Main one being that the 300d's R-12 system was not designed for the higher R134a pressures which just puts a strain on old parts making them more likely to leak. Second reason, was a legal one in Canada which requires them to completely evacuate a system that is even suspected of leaking IF it has R-12 or R134a. But this is not the case if it has HC. In latter case, it is permissible to just top up from time to time.

I asked them about contamination of their equipment etc. They said it was not a problem because they tested refrigerants to find out what they were and had equipment to recover all types. Only concern they had was if stop-leak additives were presnt because they clogged their recovery systems.

In Canada it is not legal to buy or use R-12. Nor can we buy R134a retail (unless we visit USA!). Only DIY refrigerant sold (and it is quite common), is hydrocarbon based (several makes). Major chains like Canadian Tire sell it and install it.

I have not gone ahead with A/C for 300D. They wanted $1200 for complete job of which $500 was a NEW compressor (but still of Chinese manufacture). 1 year warranty.

I don't really know what I will do. Maybe look for a junkyard compressor and install it myself either with R134a or HC. (I bought some R134a for my E-Class, but no leaks since condenser was replaced)

leathermang · #8 06-24-2010, 11:27 AM

Quote:

Originally Posted by LarryBible

... Al Gore saving us from ourselves, but now with his new mistress and inappropriate sexual contact allegations, he can no longer save us. What WILL we do???? Is there anyone else in the world that can save humanity? OH NO! WE'RE DOOMED!!!!!!!!!!!!!!!!!!!!

Larry, I am all for sarcasm where needed.... and agree with the first part of your post... but this last part was beneath your dignity and should not even have been posted in the open forum due to your total lack of verifiable facts.

Renntag · #9 06-25-2010, 11:41 PM

great thread. Much like the recent post above, I have 4 mercedes and only one has working A/C.

So in an effort to get 2 of the cars with working A/C in the next couple weeks, I want to test the system first and then flush as necessary.

Question: when considering flushing the system with acetone and compressed air, would it not be best to back flush? So then I would need to know direction of flow for each side of the system, yes ?

I will report back once I have a better idea of the status of each system.