Hey everyone its been awhile since i had any questions. But the time has come and I want to fix the air conditioning on the old benz and I'm keeping the R12 system. Don't worry we have a stash of it so that covers that base, however I'm wondering what recommendations everyone has about what to replace and inspect before spending tons of money on the AC system. Firstly the compressor has to be replaced because it has not had a belt on it since we got the car years ago and the clutch will melt the blower fuse when I turn the AC knob on in the car (the aux fan was disconnected while doing this test). Nextly, I have a spare Aux fan I'm going to install since the old one is shot completely. My plan is to throw on a compressor and a belt and charge the system and see if it even works before dumping more money in only to find out my evaporator core has a hole in it. Also before charging the system I'm going to pull a vacuum for 2 hours to make sure it holds vacuum before adding refrigerant I just wanted to specify that, if any leaks then I'll fix them. My main questions are how long should you have to pull a vacuum and also what size is the AC belt on a 1983 240D? I've heard a 13x875 belt will work but just want to double check, and of course your recommendations.

If you're opening the system, it should be flushed to get the old oil and contaminants out of the coils and hoses. You will need to empty the new compressor of any oil it has in it and install fresh mineral or PAO oil per the FSM since you're sticking with R12. Replace every O-ring in the system while you have it apart. Since the lines will be open, the filter-drier MUST be replaced. Pressure tests are typically done with nitrogen since it will not change pressure with temperature differences. Leaks will show up as a drop in standing pressure. Vacuum should be drawn to -30" on your gauge and left for at least an hour before charging. The drier you can get the system, the less trouble you'll have with it. Keep your original expansion valve, the new ones are set up for R134a and will reduce your system capacity when running R12.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

For flushing the system can you use the ac flushing solution they sell at the autoparts store? and I'm also in the process of getting a vacuum pump to do the job. I was also recommended to use ester or another brand rather than PAG since it can decrease the efficiency of R12 from a mechanic. Where can I get an O-ring kit for R12 still? and also when the whole system is working what is considered a good temp coming out of the vents? like 30 to 40 degrees below ambient temp?

Also I found a four seasons compressor (more expensive) and an ACDelco compressor (less expensive) what one should I opt for? I want a good compressor but I'm having a hard time finding one under 200$ for a mercedes, but mercedes after 1980 did use the GM R4 compressor so I guess brand doesn't matter the design doesn't change I would assume.


link: https://www.stockwiseauto.com/auto-parts/heating-and-air-conditioning/a-c-clutch-and-compressor/a-c-compressor?Year=1983&Make=Mercedes-Benz&Model=240D

You can use a flushing solution from the parts store or you can order it online. Typically there's a gun you load it into connected to an air compressor to blast it through the system then thoroughly blow it out.

O-rings are usable between either refrigerant. Get a set for your car and rock on.

R12 refrigerant must be used with PAO or mineral oil. You cannot use PAG. PAO and mineral oils will circulate with the refrigerant, PAG will find a low spot and pool, quickly ruining your compressor. Mineral oil was the original lubricant or R12 and is the preferred lube if you plan to stick with R12 forever. If you ever consider recharging with an HFC based refrigerant (R152a or R134a) use PAO oil since it is miscible with both CFC and HFC refrigerants (it also lubricates better than mineral oil).

When the system is charged and working, you should have a 30˚F split across the evaporator coil with the fan on its highest speed, all the doors open. Say if it's 90˚F ambient, you should be blowing roughly 60˚F air from the center vents if everything is right. Once the doors are closed and you're moving, the temperature in the cabin will pull down and you should be blowing mid 40s when moving, upper 40s to lower 50s when idling. Some degradation of the system may have taken place since the car was new and the big tube condensers used in the W123's aren't the most efficient, even with R12.

Window tint helps. A lot.

__________________
Current stable:
1995 E320 149K (Nancy)
1983 500SL 120K (SLoL)

Black Sheep:
1985 524TD 167K (TotalDumpster™)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Thanks I'll get to work on this project today! and post some updates every once in awhile.

Is this kit correct for changing out all the seals? its made by Santech and most other ones are conversion kits to r134a with the shraeder valves for that refrigerant. This kit has 4 shraeder valves so i would think it would provide both r12 and r134a types. Peach parts has the same kit under their own listing.

link: https://www.***************/pn/SH-227598634


peach parts link: https://www.pelicanparts.com/More_Info/227598634.htm?pn=22-7598-634-M325

first link isnt working no idea why but the second one does, both websites still have the same kit though

Mercedes up-date,the R=4 compressor was mounted up top on G/M engines,Mercedes
turned the compressor up side down and mounted on lower side of engine,now leaving
the oil lube hole to front bearing up side down,oil that used to drain down to bearing now needed to try to splash up to bearing,premature failure of bearing/compressor.
Repair: turn around front bearing plate,will need to remove clutch.
The bearing drain hole is marked on bearing plate with a small x check to see if it is on
top when mounting compressor,

Ok thanks but i do not have the tools to remove the compressor clutch and I don't want to remove it and introduce more air into the system. With all this being said I did find out I tested the system wrong earlier. The compressor and clutch work perfectly on the car, as well as the junkyard auxiliary fan I installed. After installing the new fan I turned the ignition on and the AC knob and jumped the temp. switch for the aux fan and the low pressure cutout switch and both the clutch engaged and the aux fan spun to up to speed indicating the system had no freon in it to close either switches. But now that I know this i can pull a vacuum and find leaks! also I'll post some pictures too.