I have a 1981 300SD, trying to put the a/c system in working order. The system has been down for 1 year. I have purchased a used R-4 compressor, used condensor, a new receiver dryer and a new expansion valve.
Is there anything else that I would need to replace while I'm in the process? I also plan to use a R-134 retro fit kit. Would I have to use a different kind of compressor and receiver dryer and expansion valve to complete this R-134 retro fit? And lastly where is the expansion valve located at? I want to take out the old one and replace it w/ a new one. Would you be able to provide me a step by step instructions to get to the expansion valve and how to remove it.

Thank you

GP

WOW, You are takingon a big job for a do-it-yourselfer, but I'm quite sure your up to the task. The exp. valve is located inside of the car below the dash in the driver's area. To access it you will need to drop the lower dash panel off and lay upside down on the floor. I would have used a new compressor for they are the same as on many GM cars and trucks and are cheap. The conversion is straight forward, be sure to get all of the old oil out of the system using a product such as BG FRIGI-FLUSH. Then install a PAG or equiv. oil. The new expansion valve and drier should work fine. BE SURE TO CHECK THE AUX FAN(S) FOR PROPER OPERATION.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM

The compressor is the same as GM??????
really????

So I am assuming it's a GM/AC Delco?
Would you happed to know the model # for this AC Delco unit?
Being that it is an American brand, if you can provide me some websites and prices? of where I can get them.

Thanks

The compressor is the same as GM??????
really????
So I am assuming it's a GM/AC Delco?
Would you happed to know the model # for this AC Delco unit?
Being that it is an American brand, if you can provide me some websites and prices? of where I can get them.

Thanks

compressor can be bought new for $229.95 from the benz bin (www.thebenzbin.com) You also might try the benz store at (www.benz-store.com)or any GM dealership

Good Luck

Be sure to check that your new compressor has metric threads in the mounting holes.

The pressure switch in the reciever drier should be replaced with the updated version. The new one has a cut out pressure side that will cut off the compressor if the high side pressure gets to high (approx. 450psi).

If you have an air compressor it is a good idea to take an air blower and clean out the fins of the radiator and condensor to ensure good air flow. I have seen this simple thing lower the high side pressure 50psi. Make sure the aux. fans are in good working order as they are extremely important especially when using 134a.

Remember when charging your new a/c system with 134a that the charge amount is only 85% of what the system held of R-12. Over charging the system causes reduced cooling and possible damage to the new compressor.

Hope it goes well for you and you have frost on the vents when you are done.

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MB Medic
14 year MB tech
7 year shop foreman @ independent MB/Volvo shop

If you are going to go to a GM parts source and take the old one with you be sure to check the bolt holes for metric threads...The late ones all have metric threads.

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Benzmac:
ASE CERTIFIED MASTER AUTO TECHNICIAN
LEAD TECHNICIAN FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM