Should I Add An Accumulator To The Air Conditioning System?
 

I'm currently rebuilding the air conditioning system in my 1980 W116 300SD. I'm converting it from automatic climate control to manual with parts from an early W116. I will be using refrigerant R-12, a Sanden compressor, a parallel-flow condenser, and a 16" fan from a second generation W126.

I will also be making new hoses and even though I am going to still be using an expansion valve and receiver drier, would adding an accumulator be a good idea in order to protect the compressor in the event that liquid refrigerant should inadvertently reach it? Or is this overkill and unnecessary?

I really don't want to add one, but I wonder that if by NOT adding one, I'm gambling with the life of my new polished aluminum compressor.

Since they aren't used in the factory system, I don't see why it would be necessary. Generally you only see the accumulator with orifice tube systems since they can flood back easier than an expansion valve.

It may be possible that occasionally liquid refrigerant does reach the compressor and that could be a contributing factor to why the original compressors didn't last very long. But, I don't know.

It may be a worthwhile safety device in case the expansion valve malfunctions or there is a low-load condition. I really don't want to add one, though. But, if it's one of those things where they started adding them in later years because engineers found that it prevented early compressor failure, then I'd probably want to add it (though it would be really awkward and inconvenient).

If the system is charged properly, you should have a minimal amount of liquid coming back at the compressor. If your car originally had the R4, they're not known as being the strongest design out there. The Gen II W126 still has no accumulator and the Denso compressors in them don't die like the R4's did. Your Sanden is similar construction to the Denso, so you should be in the clear.

Shouldn't be needed since I haven't seen any accumulator on Sanden kits sold for classic cars. I thought they were to minimize pulses from the compressor, but perhaps a liquid trap too. My 1969 Dodge Dart had one, on the suction to its 2-piston compressor. Neither my 1996 or 2002 has one. They have Nippondenso compressors, which like Sanden have up to 14 pistons (7 back-back), so much less pulsing. My 300D's have a large suction hose (-12) vs -8 size on most Sanden's, so that alone gives a lot of volume.

I feel better about not installing one, then.