I'm swapping engines and evaluating the A/C systems in my parts car and daily driver.

The parts car has not been driven in 2 years. The A/C compressor, condenser, manifold hose, & drier was replaced in 1998 and filled with R-12. To my knowledge the system has only ever seen R-12. There was no pressure in the system when I removed the parts, no oil leaked out of the manifold hose or the compressor. Turning the outside of the clutch to turn the shaft, it was not seized and I heard some suction going on.

The daily driver had a run in with a deer 2 months ago. The A/C compressor, condenser, manifold hose, & direr was replaced 12 months ago and filled with R134a (previously had R134a conversion by a previous owner). The condenser was damaged in the deer accident and there was no pressure in the system. Removing the manifold hose and compressor caused a puddle of oil to leak out. Turning the outside of the clutch to turn the A/C comp shaft was VERY easy to turn compared to the parts car and oil dribbled out. I did hear suction going on.

Which car is 'normal' ? I have never dealt with A/C before & do not know how easy it should be to turn the compressor shaft or how much oil should be in the system.

Thanks in advance,

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Brian Toscano

You did not say what model MB you are working on so I'll have to assume that it is the '87 300D.

That being the case, with all you said, the BIG deal here is the evaporator since it is so difficult to change. Everything else just doesn't matter much since you can replace any other component relatively easily, save maybe for the compressor.

Since I HIGHLY believe in keeping a 124 car on R12, and the car you are putting on the road is R134, this means you would have to remove the compressor to flush it and change the oil for use woth R12 so that is the same work either way.

This is what I would do if it were me. I would do everything I could to leak test the evaporator. You should be able to do this at the firewall next to the master cylinder since that's where the expansion valve is located.

Once I was happy with the evaporator, I would flush it THOROUGHLY and then flush the lines thoroughly. Then replace the filter drier and condensor after, you guessed it, a good flushing. Then take either compressor, whichever one you feel comfortable with and flush it by pouring in mineral oil and turning it by hand to get out as much as possible. Then put in the correct amount of mineral oil, use new o-rings and nylog everywhere, pump it down and charge it.

I would NOT change one of these cars to 134. All of the work you will have in it makes R12 a small price to pay to reap the benefit of your labor.

Good luck,

Larry,

I'm evaluating the condition of the A/C compressor in the parts car and daily driver (both 1987 300D's). IF the daily driver compressor has been overoiled and worn, I would rather use the parts car compressor.

I've already decided to use R-12 and may replace the evaporator at the same time because the air recirc vac element is bad and the dash will need to come out to fix that. I'm aware of the scope of the project, but changing the evap will eliminate any issues with flushing.

Thanks,

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Brian Toscano

It's hard to know which compressor is in better shape. If you make the wrong decision on this, at least it's much easier to replace later than is the evaporator.

Yes, replacing the evaporator eliminates the need for flushing, but flushing is not a big deal anyway.

Good luck with the project.'

Have a great day,