Hi everyone,
The air conditioning in my 1983 300D has suddenly gotten weak and I want to convert it to the newer R-134 refrigerant. My local Mercedes dealer (Mercedes-Benz of White Plains) wants over a thousand dollars and I really just can't afford that right now. What do you guys think of those do-it-yourself kits? Supposedly all you have to do is let all the old R12 escape, then charge it with one lb. of R-134, add the proper oil, then add three more lbs. of R-134 (so says the guy in the auto parts store). Has anyone done this before? It seems so much cheaper than recharging it with freon. Thanks for the opinions.

Alex

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1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

It seems there is not a day that goes by that I don't here or read about yet another story about a Mercedes dealer or another Shop trying to "Rip" someone else off.
Alex , yes it is true that if you replaced your compressor, upper and lower manifold hoses,Receiver dryer,expansion valve , and new R-134 fitting plus charged the system with R-134 the price from a Mercedes Dealer with their Mercedes prices would probably be more than a $1000.00 or more. But that would only be the case if all the parts in your system are bad. If your compressor is good and the manifold hoses have no holes(leaks)in them and your system will hold a good vacuum you can convert it for the price of the new fitting ($12.00) plus the charging of you system ($66.00). You will also have to have the system cleaned before you can add the R-134 because it uses a different kind of refrigerant oil(20.00) than R-12.
The ratio for R-134 is different than R-12 and most good shops go by a percentage of what your system held with R-12. Don't belive what that auto parts guy told you,you can't just add it by the can and expect it to be right,you need a good set of gages and you need someone that knows how to read and use them. It does not have to be A Mercedes dealer, just a good shop that knows what they are doing.

Do a search in the archives for AC, and you will find that this is another "popular" topic. There are many people here who have done the conversion themselves (even some who have done numerous conversions), and it's worked well for them. On the other hand, I have been told that converting to R-134a will cause your compressor to fail within two years due to the increased pressures of the new refrigerant. Also, I understand that R-134a, which is designed to work best in a newer system made to use it, will not cool as well, or as efficiently as R-12 will in your older system.

So if you still have R-12 in your system, and the system is simply getting weak, I'd go to a local AC shop that does work on Mercedes' (not all do), or find a competent independent Mercedes garage to evaluate the system. If all you need is to seal the system and recharge it with R-12, that will be cheaper in the long run...

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Scott Longston
Northern California Wine Country...
"Turbos whistle, grapes wine..."

Before switching to R134, investigate the alternative R-12. There is a great product R406 which can be used in place of R-12. The inventor george is very helpful and will discuss any and all topics pertaining to air conditioning. I took the EPA MVAC registration and then purchased some R406 (trademark name AUTOFROST). It is fantastic. It is a combination of R22 and R142b, and, as such it has the characteristics which approximate r12, only they run a little cooler (i.e. condenser is about 3-10 degrees cooler). The problem with 134a is that the oil is fully incompatible and absorbs water easily. This leads to large system failures generally a year or two after switching. R-406 does not have these problems. Just a suggestion, check it out http://www.autofrost.com

__________________
Jovan

'84 (11/83) 190D 2.2 5-Speed; Silver/Blue; Motor No. 00354, 402k mi (340+kmi mine)

'89 Porsche 911 Turbo Coupe; Black/Black; 53kmi
'05 BMW 530i 6-Speed; 302kmi
'19 Range Rover; 30kmi

DieselHead,

I hope our friend Jovan takes no offense at my response, but proceed EXTREMELY CAREFULLY regarding ANY R12 "replacement". Most of these blends are explosive. If a compressor were to lock up making a spark, you or your family will be sitting inside of an artillery shell. Yes, this has actually happened!

If you can find the leak(a flourescent dye is the best approach for this), and fix it, recharge with the gaseous gold called R12. It will do a much better job, eliminate problems and you will be much happier with the result. I have converted several vehicles to R134a and have yet to be happy with one. The 123 Benz just does not have enough condensor capacity to give you an efficient heat exchange with the less efficient R134a.

If you insist on changing to R134a, I would suggest flushing the system piece by piece, changing to green o-rings everywhere, replacing the filter-drier, using ESTER oil only, pump down for 24 hours, and charge with a volume of R134a that is 85% of the amount of R12 specified. When you screw the R134a adapters on the charging ports, don't forget to take the schrader valve out of the R12 port first.

Good luck,

I think We could start a whole new Discussion forum on just the R12 to R134 conversion topic ALONE!

Alex,

Just search the achieves for this topic and spend the next week reading the debate and make your choice.

Sorry but you will here more opinions on this subject, than theories to the meaning of life

I've done the R134 conversion to dozens with no problems.
(my opinion)

We are to enjoy life for every thing it's worth!
(My theory to the meaning of life.)

As has been stated "Stay away from R12 wanna-be replacements.

Read the post, make your choice, stay cool

Regards,
Bryan

A whole thread on this topic, hell there's a whole message board on this topic: http://www.aircondition.com

With all due respect to Larry, you should have read the link posted by jobah first. The r-406a substitute for R-12 is most assuredly *not* flammable - it contains 4% isobutane, the remainder is comprised of refrigerants just as inert as R-12 or R-134a. The flammable hydrocarbon blends (propane & isobutane) have been banned by the EPA and are no longer available.

That said, one needs to be careful when deciding to switch to an alternative. Most a/c shops only deal with two refrigerants - R-12 & R-134a. The problem is R-12 is too expensive ($37/can at my local mcparts! It was $20 last year) and R-134a doesn't work. Most shops will turn away cars filled with anything else. If you want to use one of these alternatives, it's pretty much DIY.

There are some serious hackers out there rolling their own hydrocarbon blends from camping fuel and such. Apart from the downside risks of hydrocarbon blends, a full charge of the system consumes $0.50 worth of materials. Check out the alterantive refrigerants board at aircondition.com

Larry,

I have to disagree with you on this one. True, the alternative refrigerants are flammable (propane and isobutane); R-134 is flammable too if you hit the right temperature and is toxic. You get the potential for an explosion to occur with alternative refrigerants when the a/c system is not evacuated. (i.e. compressed gas and air mixed together under pressure). If you only have compressed gas and no air there is no way for an explosion to occur even if the compressor were to seize. The alternative type of refrigerants are popular is Australia and Europe. There is alot of discussion on these alternative refrigerants at this website:

http://aircondition.com/wwwboard/alternative/


But of course the risk is left up to the individual. I believe the risk is minimal. If you were to have a head-on collision, the most likely scenario is that the gas would leak from the condenser and that is it; but of course that depends upon how hard a collision and the gas in the a/c system may not be your biggest problem but the impact itself. There are also millions of cars with gasoline tanks that have gallons of flammable gasoline and the risk is there, however slight, that if you get rear ended that fire could erupt.

Anyway, I recently had my '82 240D converted from r-12 to r-134 by a well respected european auto shop here in Houston. Am I pleased with the results? No, but it's not there fault because the 240D was designed to have the r-12. Plus it is so hot here in Houston with temps hovering around 95 degrees with incredible humidity. Also, I could not see paying to keep the r-12 refrigerant because it is false economy. The price of r-12 will only get worse, not better. Would I consider the alternatives? Yes I would. The website I listed above show posts indicating that these alternative refrigerants work as well, if not better than the old r-12 refrigerant and that there is no need to drain any a/c oil because propane and isobutane is compatable with all oils.

As for Alex's original post, the r-134 may work better in his area of the country where it isn't so hot but of course the decision is his to decide what he wants to do. But I would recommend that if he is't a DIY to take it in to have it professionally converted to R-134 because adding too much oil, refrigerant and not evacuating the system and without guages, a person would just be guessing.

Anyway, I've said enough.

Herb
'82 240D
116,000 miles

Thank you so much for all the time you guys have put into this discussion. I think you've convinced me that converting to R-134a certainly isn't a DIY job without gauges and experience, and that R-134a doesn't cool as much as R-12. So, my question is this: assuming that I don't have any leaks in my system (which I'm not sure of), how long will a R-12 charge last me? The car is a 1983 with 120,000 miles on it and I really don't know how much longer I will own this car. I definitely am willing to pay the extra to have the refrigerant that this car was meant to have and to have cooler air, but I don't want to have to recharge this system too often. I don't know when the last time the A/C was serviced because it was my dad's car and he doesn't know either.

Alex

__________________
1983 300D (parked for four years)
2012 VW Sportwagen TDI Manual
2001 Miata SE
1962 Chevrolet Corvair Rampside

Hi All,

I'm on Larry's side of the fence with regard to the R134, my car (81 300D) was recently converted to R134 from R12, bascially what I've ended up with is an A/C that wishes it could/would blow cold. Having said this, it now seems my AC compressor is now making a serious grinding noise at certain RPMs, while I don't favor my compressor going on the fritz, if it should, it will be converted back to R12, basically at what ever expense I will incur in doing so. When checking the output temp at the vent, the R134 cools to about 56 degrees F (while driving), prior to the change, it would blow at about 47 degrees F. When you consider that I live in the south with the humidity running about 90 to 98% during the summer, the extra 9 degrees in differnce by all means affects the comfort level when motoring about.

I'm hot on the trail to return to R12 as quickly as possible, as in my opinion, it's where the comfort can be found.

Thanks,
jeric

The problem is R-12 is too expensive ($37/can at my local mcparts! It was $20 last year) and R-134a doesn't work.


Doesn't work????
I must be the only one having any luck with R134a conversions. I have it in my 67 200d and my 74 280 done my old 77 450SEL, and to many other makes and models to list.

...And don't even go there, because my climate is HOT! 95+ most of the time here in Orlando .

I have a feeling that many of the DIY'ers and Pro's have indeed not preformed the conversion correctly by adding too much R134a to the system.

All I know is that it works for me....your mileage may vary, plus tax....

Regards,
Bryan

Bryan,

What temperatures are you getting out of your vents? My temperature is usually a pitiful 56 degrees. I have to drive around with the fan set on high to even feel the least bit comfortable driving around town here in Houston.

Also, did you do your conversion with a set of guages and if so, what were your readings on the guages when you put in the r-134?

Herb

My 280 has a discharge of 39 at the center vent. The 67 has a discharge of 36 and it damn near freezes me out of the car. I did not use the gauges on theses as I had broken my only set $#@%!

I just used 20% less R134 in each system to equate to the volumetric efficiency of the system compared to R12.

Example:
R12 Spec 30 ounces
multiply by .8
Amount of r134a to use is 24 ounces

The reduction equation does make a big difference in system performance. I have found converted systems that have had too much R134a in and claims of not cooling with them but, after a recover and recharge with the proper amount {minus 20%} they work fine.

Well, performance and suitability for conversion to R-134a is going to vary from model to model. MB used a bunch of different compressors (York, GM A6, GM R4, bunches of Nippondensos...) and just as many variables in the other components of the systems.

My old 123 300D could only produce 48F vent temps at highway speeds duing a Dallas summer. And that was with the recirculate function modified to use 100% recirculated air rather than the 80% the factory sets it up with! While 48F temps are just barely adequate, my opinion is that anything above 50F doesn't cut it. The car does not cool enough, and too little moisture is removed from the air - it has a muggy, humid feel to it. That's why I say R-134a doesn't work.

Those of you that have tried to convert to R134 and are getting bad results haven't done your homework. I had mine converted by a A/C guy with 40 years experience. Works perfectly. In fact better than it ever has w/R12 (granted the R12 system probably wasn't in the best shape).

1) Best site for this discussion is http://www.aircondition.com.
2) True: R134 takes about 80% to 90% of the original charge. Most A/C people are just finding this out. You have to start at 80% and watch the temp and gauges while filling.
3) Not one of you has discussed a leak detector. The dye is not as accurate as an electronic sniffer. The system MUST first be leak checked. If the system is low on R12, there is a reason and IT HAS A LEAK. Most of the early 80's MB are at an age where the compressor or hoses are dried out and leaking.
4) The ND compressors lend themselves to rebuilding. The R4 rebuild results are generally poor and don't last as long. Get a new R4, check around for prices. NEW R4 compressors aren't that much more than a GOOD rebuild.
5) If the system hasn't reached the point where the compressor is starting to disintegrate (black death) you don't need to replace the expansion valve when converting to R134. You DO need to replace the receiver dryer. Get good German hoses if any leaks are found. Don't let your A/C guy try to "make up" hoses from standard parts. If he can do this, it is certainly a sign he knows what he is doing, but between the labor and the hose material, the costs are about the same and the Euro hoses look MUCH better.
6) The condensor coil for the R134 goes across the car rather than up and down for the R12 OR vice versa, I can't remember but that is the difference. I was told there is no aftermarket R134 condensor for these older MB's. New cars have the R134 direction. So you will have to stick to the R12 style condensor. It doesn't need replacing unless it leaks. Same for the evaporator coil. Check condensor coil for bugs etc.
7) The system needs flushing out prior to the conversion. Special fluid is used to clean and flush.
8) My system conversion took all day by a pro. New compressor, 4 new hoses, new receiver dryer. Didn't need 24 hours of vacuum.
9) In closing: get the system leak checked with the electronic leak detector. Skip the dye. Replace the leaking parts. Flush, change Receiver/dryer, vacuum, replace w/R134 oil, charge system with gauges and start low on the # of lbs. I agree with Larrym if the hoses are OK, replace the hose seals anyway. Find a good A/C guy. I'm in Los Angeles so this wasn't hard.