A/C repair. Thanks to Benzmac, et al. - PeachParts Mercedes-Benz Forum

JRBrown · #1 10-19-2002, 01:30 PM

To all who have contributed their advice and counsel regarding R12 vs R134. THANKS!!!

Just had my 22 year old AC compressor, dryer and expansion valve replaced on my 1980 450SEL. Clutch failed catastrophically along with a leak in a compressor seal. Not to bad to have lasted 22 years.

Found a reputable independent willing to let me bring my own NEW parts as he does not do many BENZ's. Had it all flushed, replaced all O-rings with R-12/134 compatiable rings and oil, and then went ahead and installed R12.

I viewed the R12 advice from past posts as the most reasonable thing to do. The darn system wasn't designed for R134 without a few more mods (e.g. automate the cooling fan to come on sooner, etc.) Heck, At least what I did leaves open the opportunity to install 134 later if necessary.

Again, This is a top 3 web site for me. THANKS!!! (OBTW - FastLane is GREAT!!!)

Ockman · #2 10-20-2002, 07:18 AM

Congrats...I think you made the right decision. I switched to R134 when I replaced the compressor, o-rings and receiver dryer on my 83 300D and was not satisfied. It worked well as long as you were moving, but in stop and go traffic in Florida it could not keep up. I went back to R-12 and all was well again, even in Miami traffic. BTW, the price of R12 seems to be tapering off a bit as the number of vehicles using it are diminishing. Good luck.

#3 10-20-2002, 11:01 AM

This IMHO was a very wise choice. I'm glad everything is back in good shape.

If you now experience another leak, immediately put UV dye in the system to help find it. If the system was evacuated properly, the chances of another leak are very low.

Good work,

BDBENZ · #4 10-20-2002, 02:22 PM

My 87 560 was converted to r134 by the MB dealer when they replaced the condenser & new drier. It seams to cool OK, especially here in the Midwest. My compressor is a little nosier than I am accustomed to hearing. Is this normal for r134, and does R-12 and mineral oil allow the compressor to operate quieter?

How difficult would it be to convert a unit from R134 back to R-12?

Thanks,

BD

JRBrown · #5 10-23-2002, 08:18 PM

Larry,

Thanks for the advice on the potential for a leak. I purchased an electronic leak detector to chase two leaks in two other vehciles in the stable. Found both in a matter of minutes. Best money I've spent on a tool in a while. After I run the 450 for a week or two, I'll go over it to make sure all is secure.

I was all prepared to get my license and I found that I can't buy R12 at AUTOZONE or anywhere else here in Southern Maryland. Mailorder only.

B.D.

134 to 12. Basics are:
-Listen to folks like Larry Bible and Benzmac (lots of wisdom there)
-Whoever converted it for you should be able to tell you if the oil is 134 and 12 compatiable. My guess is that it is. However, you need to probe as to whether or not if he pulled your compressor to drain the oil. I am told that flushing a compressor is bad.
-As long as there were no extra switches installed and the expansion valve is the correct orfice size your mech should be able to recover the 134, pull a vacuum, and load 12.
- Regarding the noise, I suspect that the higher pressures are contributing.

Any other folks out there that went back to 12?

BDBENZ · #6 10-23-2002, 10:18 PM

The MB dealer did the repair and conversation, it was completed according to MB recommended procedures. It does not appear from inspection that the compressor was removed. I know that the system now has PAG oil, and understand that this is not compatible with mineral oil?

It cools fine, I am concerned with the longevity of the compressor. What would you recommend as the correct procedure to return to R12, or since it is now converted, leave it alone.

BD

JRBrown · #7 10-24-2002, 05:44 PM

BD,

My first order of business would be to have the mechanic confirm that the oil is R12/134 compatiable. It most likely is compatiable.

Then find out if the desiccant in the R/D is R12 compatiable. It most likely is.

Lastly, find out if the expansion valve was changed out and why. I haven't heard of many R134 specific expansion valves for conversion purposes. If it was changed out it was probably done with the seal changes (if it uses seals vice copper seals) since it had to come off any way and they aren't normally very expensive.

Since the system is probably not leaking, it would then be a matter of a pull down, and recharge with R12.

Compressors aren't cheap, and one working too hard will fail sooner. Benzmac hit the nail on the head for me. R12 is the least expensive component in the A/C chain. Why mess with a good thing.