Mercedes Benz repair: air conditioning compressor replacement, air conditioning compressor, auto mechanic

Question
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Followup To
Question -
vehicle in question: 1984 MB 300D (123 series)

Tim Graney: Thank you, thank you, thank you for such quick response. Hope you can indulge one (last) quick follow-up:

THE "EXPANSION VALVE" WHAT/WHERE IS IT AND WHY IS IT IMPORTANT? IS THE EXCHANGE FOR NEW ONE FAIRLY STRAIGHTFORWARD AS COMPRESSOR APPEARS TO BE?

THANKS AGAIN, MIKE

I would like to replace the A/C compressor unit in above vehicle.
I have chiltons guide for compressor unit itself but need guidance on expansion valve replacement, etc.
Is there a step-by-step guide to all phases of the replacement for one who is not an auto mechanic but with some mechanical ability?
Thank You, Mike
Answer -
The only thing you need to be careful about is removing the lines to the compressor itself. The R12 is compressed and is fairly toxic. Do this in open air and crack the line slowly to release the pressure. Once the pressure is released it is pretty straight forward. Once the compressor is removed be careful not to spill the oil that is inside the compressor. The new compressor will have no oil in it and you will have to switch to R134. Make sure you have this done by a qualified technician. They no longer support R12. The other thing to be careful of is to replace the copper seals in the lines. You do not want any leaks of the AC will not work very long and it can get quite expensive replacing the R134.

Answer
The expansion valve is located with the evaporator. This will be under the dashboard on the passenger side. It is a bear to change. You have to remove the whole unit to replace. Some AC people say you must change the expansion valve to accomodate R134. I have done the chageover without changing the expansion valve. The only thing you might want to replace are the seals in the expansion valve.