W123 AC Compressor & Filter Dryer Replace - PeachParts Mercedes-Benz Forum

tobybul · #1 06-18-2007, 09:17 AM

Planning to replace these parts and wanted some advise from those who have done it. Does not seem to be that difficult of a job to do but I don't know that for a fact.

System has been converted to r134 and plan to keep it that way. Was not planning on replacing the expansion valve.

Present compressor clutch is not working very well anymore. The thing squeels really badly. Thanks

Kuhlrover · #2 06-18-2007, 11:21 AM

I did the same job you are describing a couple of years ago when the front seal went bad on my R4 compressor. There are no tricks to replacing either the dryer or compressor. It does take some patience and some grimacing to get the compressor hefted in place if you are doing it by yourself. It helps to have someone supporting it from the top while you are installing the first bolt from the bottom or visa versa.

1. Take it to your local A/C shop and have them reclaim the existing R 134 charge. They should reclaim the refridgerent but not pull a hard vacuum unless they bring it back to atmospheric pressure with nitrogen. You don't want moisture laden atmosperic air being drawn into the system when you open it up.
2. First do the compressor. This way any moisture that does enter the system doesn't immediately attack the desicant for the new dryer. (You may think you will have the hoses off for a couple of hours until you drop a bolt, cut an O ring or something else and all of a sudden the system is open for a couple of days.)
3. Remove the old compressor and drain as much oil out of it as possible into a glass measuring cup. (Take the glass measuring cup your spouse uses for cooking and then keep it in the garage. Tell her you contaminated it will replace it.)
4. Unplug the fittings on the new compressor and drain the oil out of it. Even if it has a tag that says it is shipped dry, I have found this to be rarely the case. Re-install the oil into the compressor to the same amount that was taken out of the old compressor. Use any oil left over to lubricate any of the new O rings.
5. With the pulley side of the compressor facing down, the ports unplugged, the clutch held in place, rotate the compressor 10 complete revolutions in the same direction the compressor would turn if it was on the car. I used my vice for this where I open the jaws just wide enough to keep the triangle shaped brace on the front of the clutch from moving when I rotated the compressor body. I did not clamp the vice on this. Of course in this configuration you are turning the compressor and holding the clutch where as when it's on the car the compressor is held still and the clutch turns, so you will have to do the mental gymnastics to rotate this in the proper direction. As you turn the compressor body you will notice one of the ports sucking and the other blowing. Pour the oil in the sucking port. This step is necessary to properly lubricate the front seal at start up.
6. Lubricate the O rings and install the compressor.
7. Replace the dryer. You will need to transfer the temperature sensor and the low pressure switch.
8. Drain the oil out of dryer. If none comes out, that is ok. What does come out needs to be measured and the same amount of fresh oil poured into the new drier.
9. Take it back to you local shop to be evacuated, checked for leaks and recharged.

Good Luck.

TimK