1989 300E A/C questions

[Tassie]

I have no cold/cool air generated by my 300E's air conditioning. The system seems to have failed over the winter as last summer the system cooled very well. I went to a reputable A/C repair facility and they said there was not enough refrigerant in the system to test the system. As well, they couldn't tell where the leak was because of low refridgerant and there was no obvious leak at any visible fittings. As they were not familiar with the Mercedes A/C process they declined to do further work and advised taking the car to the dealer. The dealer stated it would take 2 hours and $200 for diagnosis only. Repairs are extra.

The A/C shop stated that I have to recharge the system just to find where the leak is. Being in Canada - this also means conversion to R134 refridgerant. Although there is plenty of advice to not convert - this may not be a viable option as I would have to travel to the US for this work. I presume that I can live with reduced efficiency of R134 but I am concerned with the remaining longevity of the A/C components? Is it worth driving the 200 miles to the US to keep the system with R12? Besides being recharged what else should be changed out or checked when the work is being done? It appears that the prevailing advice is to change, at least, the drier/dessicant canister. I'm hoping that the leak is minor and accessible!

I've read lots on this website on Mercedes A/C and now just would like some comments on how best to proceed with my problem.

Thanks for the help!

Regards,
Paul

[Panzer_Man]

I will offer my tiny slice of knowledge on the subject:
R134a is much cheaper as you know; it'll probably pay to convert sooner or later if you plan to keep the car, especially if they pump it full of expensive R12 and it leaks out during testing. I'm not even sure you can get R12 very easily here in the US and if so, it's PRICY.

Always change the drier with compressor, yes.

I live in hot Florida and my R134a-fed system cools okay. But the compressor is dying after only 16 months for what's it worth. Don't know if it has anything to do with R134a but doubtful.

Finally, compressors, seals etc..., are lubricated by the system. Run it regularly even if you don't need it. HVAC guys will tell you once a week. Maybe not that often but at least crank it up once a month.

[stevebfl]

The price of R12 is only about 50% greater than R134 this summer. R134's price has risen about 400% since last summer. Cost is even less of a reason.

[Tassie]

I have a few more questions....

1) What is the process for finding a leak if there is not enough refrigerant left? This being an R12 system and we can't get R12 in Canada - what material will be used and will it contaminate the system to prevent R12 from being used again?

2) Is there any danger to the A/C components when running with mimimal refrigerant? Am I correct in presuming that the low/high pressure cutout at the receiver/drier protects the system? Because of budget concerns I will probably have to operate the vehicle a couple of months before I'm able to get the repairs done.

3) After reading about "Black Death" - it scared the hell out of me! Some articles suggested the installation of a filter to catch any particles if a compressor happened to fail. Considering the damage that "Black Death" causes and the significant cost of these repairs, adding a filter makes sense. Can a filter be installed? Where should it be located? I think that between the compressor and condensor makes sense. Who makes these? Will it decrease A/C performance? Some articles describe the receiver/drier is a "filter" but I think the context is for filtering moisture not particles. Any thoughts on all this?

Thanks all,
Paul

[aqua190]

1) On my system, they filled with 134a to check for leaks. Evacuated it out and refilled with r-12 after determining the system was leak free. Since you live in Canada, I don't know if this is an option for you. If you come over to the US to get it done, I think your best bet is a custom a/c shop. One that does RV's, Classic Cars, and the like. They seem to appreciate the benefits of r-12 over 134a. Most car shops have ditched their r-12 equipment as it breaks since 134a is the dominant refrigerant now and are more interested in converting to 134a.

2) Running your system when it's low on refrigerant isn't a good idea. Yes, the low cut out will stop the compressor once it's threshold is reached, but refrigerant carries the lubricating oil through the system. If you're low on refrigerant, sufficient oil is not being carried through the system.

3) I believe the filters are usually installed on the suction line, before the compressor.

You may help hold your costs down by purchasing the parts before you make the appt with the a/c shop. Go ahead and get the rec-drier, new aux fan swx, low pressure cut out switch and the needed O-rings as well. Fastlane and other online vendors supply them. The filter can be purchased from ackits.com

Good Luck

[Mike Murrell]

I do not do this for a living, but will offer my take on it anyway.

- Normally I would suggest that you keep an R-12 car as an R-12 car. I believe that cars coming from the factory as R134a do quite well, but they were built from the ground up as R134a cars. Unless the entire system is changed out during conversion, you have a mixed-bag of R-12/R134a components.

- Some say that the heat transfer capabilities of R134a is not as good as R-12. That may be the case in a converison scenario. I have a 2004 base model Tacoma pickup equipped with R-134a(from the factory) that blows 40F air on a 100F day. Go figure. BUT....you live in Canada and I doubt you have to deal with the temps that exist in the lower half of the U. S.

- I respect Steve Brothertons and Larry Bibles observation about the drop in price of R-12. Having the credentials to purchase said product, I am now paying about $10 a can less for R-12 than say a year ago. It has indeed dropped in price. BUT...you might be considering a trip to the U. S. where a shop would repair the leak(hopefully) and recharge. Larry has mentioned $14 a lb. R-12. In cans(from Larry' source), it's a hair over $20. Not too bad considering the rising cost of R-134a. Now comes the hard part.....getting a shop to sell you R-12 at a price that's even remotely resonable. I know for a fact that shops that still service R-12 systems(they are growing fewer and fewer as time goes on) charge WAY more than $14 a lb. You wouldn't believe the price being charged in a lot of these places. You'd spend some big $$$ recharging with R-12 and then be faced with the possibility of a return trip at some point in the future.

- SO...unless you plan on coming down yonder and studying for the 609 exam(not sure a Canadian could do that?) and finding/fixing your leak in a hotel parking lot, I personally believe you would be better off converting to R-134a.

Your circumstances just don't support an R-12 conversion.

My 2 cents.

[samiam4]

You need someone to leak test the system.

You cannot do this with a partial charge. You could pressurize it with N2 and a little freon, then leak check it. Or you can fill it up with R-12 and test it.
Then, they will evacuate the system and fix the leak.

As a rule I wouldn't convert an R-12 car, but being in a country where R-12 is not avaliable presents a new level of problems. If you convert it- do it right and flush the old oil from the system. Put back a R134a oil , replace all the rubber o-rings, a new dryer and expansion valve. Then go.


Michael

[Tassie]

Well, the local dealership found the leak - it was a cracked condenser near the bottom (near outlet?). Obviously, the condenser will have to be replaced.

I've read through lots on A/C in this forum and it appears wisest to maintain the system as an R-12 system.

What options do I have with a new condenser for my 1989 300E? Is there a parallel flow model that I can use? Or will the 1989 style replacement be satisfactory?

Replacing the receiver/drier is virtually mandatory. No issue with that.

I've also read that on a car this old that it is wise to replace all the O-rings. Are they present at every thread fitting? I'm a little hesitant to open fittings on a 16 year old car lest I damage the pipe (ie the evaporator).

Would it be prudent to replace the hoses? This is an expensive option as one of the hoses has the fuel cooler attached.

Would it be prudent to replace the expansion valve? This part is not significantly expensive but access and age concern me for potential cracking or other damage.

By the way, the dealer recommended that I repair with STOP LEAK and convert to Duracool. Total repair and conversion cost was quoted as $1500 CDN. Sure glad that I was well informed by this forum. This won't happen!

Look forward to your replies so that I can collect parts and schedule repair time.

Thanks all,
Paul

[jcyuhn]

The stock condenser is fine, I recommend you stay with it. It is possible to convert to a parallel condenser, but you are looking at a whole bunch of custom work to do so. A generic parallel condenser won't use the stock mounting points, so you would have to fabricate the mounting. Also, the inlet & outlet fittings are in different locations (and likely different sizes) so you need to have custom hoses made up. It can be done, but it's a bit of money and a bunch of time and effort.

Given that you reside in the great white north, I'm going against the grain and recommending a conversion to R-134a. It's just not going to be worth the hassle to trek over the U.S. every time you need a/c service or a refrigerant top up. When correctly converted, R-134a works better than expected in these cars. I ran it for a while in my 1987 wagon - in Dallas, in July. It was surprisingly adequate. The key is to insure the entire system is up to par. Replacing the condenser is a good start. Another important step is to insure that your recirculating air door works - the a/c is much cooler when recirculating air through the car than when sucking in hot, humid outside air.

Replace the expansion valve and associated o-rings. It's a known leaky point on these cars. Need to do the one on my spouses 1993 300E, actually. You'll need to pull the exp. valve to flush the evaporator prior to conversion anyways, so there's no extra labor required.

My $.02,

- JimY

[lyonstexas]

I would recommend that you replace the Schrader valves while doing the other work. Inexpensive and a source of leaks.

Tim

[Tassie]

Thanks for your responses to my previous questions. I have a couple of clarifications, please.

The repairs will probably occur in a month or so which means that the A/C had no refrigerant for about 10 months maximum. Does this have an influence on how I should approach the repairs? Remember, this is a 16 year old car with about 120,000 miles.

I will have the system open to replace the condenser, receiver/dryer, expansion valve, O-rings and Schrader valve seals, and recharged with R-12. This is a fair amount of work already. But, what about the compressor especially the seals? I believe this is the compressor shaft seal. Are there other seals on the compressor? I presume the A/C line manifold at the compressor has O-rings, which will be replaced. As far as I know the compressor is/was working fine and gets occasional use (say, 1 hour every two weeks).

Is replacing the compressor seal(s) a wise step? Will this add considerably to the repair time and cost? Would it be more prudent to replace with a rebuilt compressor for a 16 year old car? I want a respectable repair and I am willing to pay for what needs to be done right. However, I can't afford to throw money at the repairs but neither do I want to come back in a year to fix another leak that could have been easily repaired the first time (evaporator excepted).

Thanks again for your help!
Paul

[samiam4]

Paul,

That's a good question on the compressor! I believe there is information lurking in this group on buying a seal kit from Toyota. The aftermarket kits are well-less reliable. I was thinking there was a body o-ring which leaks sometimes. If you pull the clutch and replace the seal. The clutch plate clearance is pretty critical for the system to operate correctly. Hence, re-shim the clutch as required.
I haven't been down this road in YEARS, but maybe traveling here soon. Hope this is helpful.

Michael

[Tassie]

Well, I had the opportunity to travel to Portland, Oregon and took the car to MBI Motors as they were very well recommended. Before replacing the condenser I asked them to verify that the condenser was leaking. This was a good decision as MBI put the A/C system on a pressure test and the system did not leak at all even overnight. Therefore, all they did was top up the refrigerant and verified the operation of the system. I now have a working A/C system for $144US which was significantly less than the $6-800 I was expecting. They were cautious of the condition of the system as the car is now 15 years old but stated that it was best to leave things well enough alone and recommended to not do any other work until necessary. I'm comfortable with their recommendation as the car is in pretty good shape and I don't anticipate any problems soon.

Regards,
Paul