My A/C has lost its charge. I am 80 miles from my trusted indy Benz mechanic. Serious illness of a close friend precludes my having the full day it would require to drive the distance and wait around to have my unit serviced. I have read many threads from my search, here, and am totally confused.

There is a trustworthy mechanic just up the road from me who says he can charge the system with R-12, R-12 oil, and check and repair any leaks.

My problem is, will regular R-12 oil work in my 116? I have seen threads regarding mineral oil as a lubricant. I can't afford to screw up a compressor, and don't want to come off as a know-it-all when I explain to this local tech how to properly charge my system.

Please help.

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1980 300SD 146K miles.

The only oil used for R12 was mineral oil. When the conversion craze started another oil (ester based) was introduced to go both ways. Unless he just keeps ester to work on everything it is likely he will use mineral oil as it is much less expensive.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

Thanks for that prompt reply. I did not know that mineral oil was the common R-12 lubricant, and feared it was another quirk such as MB anti-freeze, etc.

It is already into the high 80's, here, and I need to get that unit up and running.

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1980 300SD 146K miles.

I would suggest on an emergency deal like that that the Reciever/Dryer be replaced... with the right amount of correct oil placed in it ....of course...because the theory is that any leak means air/water vapor cantamination in the system... replacing it this emergency fix may help because you are not flushing.. and the moisture which has gotten into the oil...and been caught by the dessicant in the R/D is not subject to evacuation (vacuuming of the moisture out)....
At some time when you have more time... to safeguard the compressor..... since when you have a leak typically you lose oil with it..... and therefor do not know how much oil is in your system... that at some point you have the system flushed, and refilled measureing the amount of oil put back in...
too much oil is bad and too little is bad....

Thanks, Leathermang

Let us assume my local guy has the knowledge and equipment to flush the system, and I get a new R/D from Fastlane. What would be the proper flushing method, and how much oil would be just right?

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1980 300SD 146K miles.

Too much oil is real bad. I would be real conservative in how much oil you put in a system with an unknown quantity.

I would never put a full oil charge in a system that hadn't been thoroughly flushed. There are standard quantities in the manuals for anticipating what the proper proportion of the full charge resides in each device. The only way I know of addressing the oil quantitatively is to measure the oil in one of the devices and relate the quantity to the original disposition. Then use the same percentage on the total charge and replace the difference.

The best way to do this is to measure the oil in the compressor except many MB compressors have no oil reservoir.

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Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician