1989 W124 A/C Repairs/Rebuild/Upgrade

[Tassie]

I'm planning to do some air conditioning upgrades when funds allow.

The original 1989 R-12 system worked fine until a couple of years ago. The system worked well for about 16-17 years or about 180,000 km (110,000 miles) and I would like to do a good quality job. Being in Canada, I do not have a legal source of R-12 to recharge so I have to work with R-134a. I don't wish to attempt any other form of refrigerant.

The A/C shop could not conduct any refrigerant pressure tests because there was nothing in the system although a 12 hr pressure test did not indicate any leaks.

That being said - I am willing to put some effort and expense (but not excessively) into getting the A/C system working and improved. It appears that I could do this by converting to a parallel flow condenser, replacing the A/C hoses, installing a rebuilt compressor, new drier, and possibly the expansion valve. The evaporator will stay as is unless I really have to replace.

My questions are:

1) Is there a W124 parallel flow condenser that will directly replace the original condenser? Is this a custom job and, if so, how big a job is it?

2) Replacement A/C hoses are reasonable cost EXCEPT for the fuel cooler line. Can the hoses on this device be replaced with the new barrier hose? Or do I have to buy the whole thing? If installing a parallel flow condenser do I have to install modified hoses? (ie a bit longer or different routing)

3) Is it worthwhile to replace the single aux fan with the dual fan setup of later W124's? I suspect the dual fans increase the airflow over the condenser to improve cooling capacity but is it worthwhile? How big a job is the replacement?

4) Should I stay with the originally spec'd Denso 10p15c compressor or is there a better model (greater capacity) that can be effectively used.

5) Are there any other parts that I should consider in this rebuild and upgrade plan?

I would really appreciate some assistance with these questions so I can start collecting the parts and then plan getting the work done.

Many thanks in advance,
Paul

[TCG]

Paul,

Don't go crazy here. I've converted a 123, 124, and a 126 to 134a and have achieved good results each time. The 124 was a 1986 300E. When the evaporator started to leak (it seems they all will) I replaced it, removed as much of the oil as I could, evacuated, and charged with 134a. It was not quite as cold as the R12 system but it worked fine. Keep in mind I live in Florida where the humidity and heat load from the sun is very high.

I eventually removed the pin from the visco fan clutch which locked it up at speeds under 3000 RPM. This car was used almost exclusively in town and the extra airflow improved the system at idle.

If your compressor is good, leave it. The hoses will be fine. They are impregnated with oil which will be a barrier for the 134a.

So:
1. The parallel flow condenser. If you feel you must but I wouldn't.

2. No reason to bother. I ended up topping off my cars of every 2 or 3 years.

3. Just make sure the fans work properly.

4. If the compressor is good, use it.

5. New receiver dryer, new expansion valve, suck down the system for at least 1 hour, and I think you will be happy with the results.

Any residual original oil will find a low spot and won't be a problem. Don't over oil the system with PAG oil, use the amount recommended by MB. Charge with 134a to about 80% of R12 charge. It seems a little under is better than over.

This is not a big deal, conversion is straight forward. My 89 300SEL is pretty darn cold. My wife is happy and she hates the heat!

Good Luck,

Tom
92 500E pearl gray
92 500E black pearl
89 300SEL needs paint

[Tassie]

Hi Tom;

Thanks for the reply. I appreciate your points and will consider.

I might have a leaking condenser although the pressure test did not indicate any leakdown. I think that I might redo the pressure test and look at all the fittings much more closely.

If I have to replace the condenser then I may as well install the parallel flow condenser. My understanding is that the increased cooling area of the PFC offsets the reduced capacity of the R134a to absorb heat. However, I'm not sure of the part number (is there an OEM replacement?) and the fitting (mounting holes, hose connections, etc).

I wasn't planning to do this immediately. I am hoping to economize by collecting the appropriate parts as they became available on-line (Ebay, Craigslist, etc) or at the wreckers.

Thanks,
Paul

[Mr Project]

I know on my E34 BMWs, the later models that came from the factory with R134a had a slightly larger (though not parallel flow) condenser to make up for the reduced cooling capacity. That makes for an easy upgrade since it's already set up for the existing mounting points and hoses.

I wonder if a condenser from a 94-95 W124 (with an R134a factory fill) would be a similar upgrade for you? I would imagine it would be much less work than fabricating the hoses and mounts needed for an aftermarket PFC.

[david s poole]

you live in canada,it doesn't get hot enough to go to those extremes.just remember that molecules of 134 are smaller than 12 so that if evaporator not already replaced will need to be done because of epoxy seals on u tubes[134 will find a hole and enlarge it very quickly]

[remotemark]

Originally Posted by Mr Project

I know on my E34 BMWs, the later models that came from the factory with R134a had a slightly larger (though not parallel flow) condenser to make up for the reduced cooling capacity. That makes for an easy upgrade since it's already set up for the existing mounting points and hoses.

I wonder if a condenser from a 94-95 W124 (with an R134a factory fill) would be a similar upgrade for you? I would imagine it would be much less work than fabricating the hoses and mounts needed for an aftermarket PFC.

That would be a great upgrade for my converted 124. I'd love to get a proper condenser in there if it didn't need to be made to fit with specially fabbed fittings and hoses.

[remotemark]

Originally Posted by Mr Project

I wonder if a condenser from a 94-95 W124 (with an R134a factory fill) would be a similar upgrade for you? I would imagine it would be much less work than fabricating the hoses and mounts needed for an aftermarket PFC.

Any 124 experts out there know if you could plug-n-play a 94-95 condenser in an earlier 124 which has been converted to 134 but needs to produce colder air?

I hope I don't come off condescending here, but I DON'T GET IT! Why would you want to do all this work and go to all this expense with PF condensors and all sorts of dollars spent so that you can save $40 or $50 on refrigerant?

This sounds like the accounting methods used by the US Treasury Department!

You have already tested and found a leak free system. Add an ounce or two of mineral oil, evacuate thoroughly and recharge with R12. This will cost you a fraction of what all this work you're proposing and give you the system that was designed into the car with the refrigerant for which it was designed.

BTW, the evaporators in these cars do indeed have a reputation for failure, but don't buy into the notion that it is GUARANTEED to fail. My car is 21 years old with 310,000 miles with the original evaporator and NO leaks. It will make a Polar Bear scream for mercy and I live in Texas.

[Tassie]

Hi Larry;

I think you're right but there are several issues at play. Please bear with me.

One, the AC system is not working again therefore I am planning my options. I cannot legally obtain R-12 in Canada so for the ease of legally maintaining the A/C system I have to consider converting to R-134 refrigerant.

Two, I may have a leaking condenser (but not yet confirmed) so if that is the case then I want to consider replacing with a PF condenser but only if it easily installed (ie were those W124's equipped with R134 refrigerant also equipped with PF condensers or larger condensers to offset the lower efficiency of R134?). I have no desire to re-engineer an aftermarket condenser with new attachment brackets, new AC fittings, and new routing for the AC hoses.

Three, I had the understanding that replacing the A/C hoses was required when converting to R134. I have since read and confirmed by others that older hoses that have used R12 may be "sealed" therefore hose replacement may not be necessary. But if it is a source of leakage then new hoses are relatively inexpensive EXCEPT for the one hose with the fuel cooler. As new hose is worth about $10/ft I wanted to know if I could simply replace the hose and the crimp fittings for this particular item.

Four, I was looking for a long term repair not simply patching the system year after year. Of course, patching the system may be the most economical approach but if long term repairs can be done economically then why not do it right in the first place? Please note that I have no intent of throwing a pile of money at this. If repairs are necessary then I want to consider the long term options, the cost and the benefits for long term efficiency and reliability, make my choice, and proceed.

Five, if it is possible and also economical then improving the efficiency of the system is also desirable (for instance, is converting from the single fan to the dual fan an easy job? Looks easy but I may be wrong). However, I don't have all the answers (hence the questions) so I couldn't determine if improvements are easily available and cost-effective.

I hope this clears up why I am asking the questions. So far, it appears that leaving the system "as is" is the most appropriate course of action especially for those that have legal sources of R-12. I may have to simply live with the reduced efficiency of R134.

I certainly appreciate the advice and feedback.

Cheers,
Paul

[amosfella]

Well, I'll give you a quick opinion... You say you're not willing to look at alternatives. BUT, I think I can make a case for it...
Here in Alberta anyways, you can buy a R12 replacement called R12a very easily, and cheaper than R134a. It's about half the price. It has a larger molecule than R134a, and also runs colder at lower pressures. By lower pressure, we're talking about half the pressure of R134a.
Also, you apparently don't have to vacuum the system to almost nothing either. 10 in hg is enough according to the manufacturer. They guarantee that it's noncorrosive. Something R134a cannot claim.
Also, if there is a leak in the system, You can buy one of their 2 stop leak products. One is for rubber, and the other is for metal. I know many people who use it in their vehicles here, and it works quite well, in one case, a tractor of ours was leaking down every week. We put the stop leak in, and it's been 3 years since we filled the system. It still blows really cold.
Redtec and duracool are two companies that make R12a. It's completely compatible with the R12 system, and the oil used in there.
Because I couldn't get the small cans of R134a ANYWHERE around here, I sucked the R134a out of the system and put in Duracool R12a. I can buy that stuff at the local family owned hardware store. Every machine dealer, mechanic's supply, and parts counter around here has it. Even Walmart sells it.....
If you want R134a, you have to take a test and wait 2 weeks for a license, and then you get to buy a 30 lb cylinder. So, if you want to take your AC refills to the mechanic shop every time (and if it's leaking, it will be more and more often), I would just use R12a and be done with the whole mess.

I am NOT a fan of what I call JUNK refrigerants, but in the case where R12 is illegal, the proper JUNK refrigerant might be a better alternative than 134.

Because I will not use them, I am not an authority on the various junk refrigerants, but faced with such a situation, I would find one that worked with the mineral oil already in the system, add an ounce or two of mineral oil, evacuate and charge with the alternative.

If you are looking at an alternative refrigerant, you need to be aware of some things. ALL JUNK refrigerants fall into one of two categories; flammables and blends.

The downside to flammables is obvious, what is not so obvious is that most of them will have a moisture content that cannot be removed because evacuation is done BEFORE the refrigerant is fed to the system.

The downside to blends, which should be your only alternative, is that if you get a leak, the components leak at different rates, upsetting the balance of ingredients. For this reason, when the system gets low, you must remove the remaining refrigerant, fix the leak, evacuate and recharge.

[remotemark]

Originally Posted by LarryBible

You have already tested and found a leak free system. Add an ounce or two of mineral oil, evacuate thoroughly and recharge with R12. This will cost you a fraction of what all this work you're proposing and give you the system that was designed into the car with the refrigerant for which it was designed.

Unfortunately, my 300CE was converted to 134 long ago and I can't just put R12 into it.

remotemark,

Reverse conversion is not that difficult. I would not suggest doing it on a working, converted system, but when it comes time to make a repair on the system and the refrigerant is being recevered anyway, simply do whatever repair is necessary, flush the system, replace the r/d, put in the correct amount of Mineral oil, evacuate and charge. There are now some synthetic oils that work quite well with R12. It would be a good time to go to one of those products as the lubricant in place of the mineral oil.

I have done several reverse conversions with great success!

[ajme]

Tassie;

I converted our 1989 190e to R134a six years ago, and it has cooled well ever since, with no need to recharge it yet. No fancy upgrades. But I did replace: the compressor (leaking); the expensive hose with the fuel cooler (leaking); the receiver-drier; the expansion valve; the pressure switch (added a dual switch); all the o-rings; and installed the new ports. It ended up being quite expensive, because of the compressor and the hose.

The Mercedes guys under the Oak Street Bridge tested the system for me and found the leaks.

Paul (the younger Paul) at BMV on Bridgeport Road in Richmond knows exactly what you need for the conversion.

Andrew

[remotemark]

Originally Posted by LarryBible

remotemark,

Reverse conversion is not that difficult. I would not suggest doing it on a working, converted system, but when it comes time to make a repair on the system and the refrigerant is being recevered anyway, simply do whatever repair is necessary, flush the system, replace the r/d, put in the correct amount of Mineral oil, evacuate and charge. There are now some synthetic oils that work quite well with R12. It would be a good time to go to one of those products as the lubricant in place of the mineral oil.

I have done several reverse conversions with great success!

My mechanic is un-converting my 300CE this week. However, even if I provide to him the three cans of R12 I have sourced but not procured, he will not use them. Instead, he proposes to use Freeze12. I know you view that as a JUNK refrigerant. My question is whether I could at some point replace the Freeze12 with R12 without anything other than an evacuation and re-charge.