Totally confused here about A/C system. I have 1988 300 SE. Am I right in thinking that since I have a receiver drier, I shouldn't have an expansion valve? If I should have such, where is it located? Pics would sure help. Thanks.......

Expansion valve will be near the evaporator beneath the dash.

http://www.funnyyouasked.com/Mercedes/W126/ExpValve/removal_and_replacement_of_expan.htm

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1989 300CE

Thanx mbzman for that answer about the expansion valve. I've noticed different colored ( black and green) O-rings used in the A/C system connections. Is there a difference? I'm repairing an R-12 system.....