With the engine OFF..... and your hand on the compressor clutch... when you pull the leads off do you hear or feel a click ?
With the engine OFF..... but with the ignition switch on and the AC switch on ... do the same test... do you hear or feel a click ?

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1980 240d ,

chain elongation, cam marks reference:
http://www.peachparts.com/shopforum/showthread.php?threadid=10414

http://www.peachparts.com/shopforum/diesel-discussion/305365-9-degrees-chain-stretch.html

evap fin cleaning:

http://www.peachparts.com/shopforum/showthread.php?t=156207&highlight=evaporator

A/C thread

http://www.peachparts.com/shopforum/diesel-discussion/297462-c-recommendations-mb-vehicles.html