There are a lot of relays and vac hoses and electrical connections that affect the CC and some of the problems can be in the switches behind those CC dash buttons and dials ..... that is the most difficult system to diagnose, but not as bad as my 76 450SEL, which has a servo system out in the engine area that controls all the hot water and AC etc etc ..... You just have to check every connection and subsystem --- which can be a daunting process.
Sometimes a minor fix or contact cleaning can be the cure .... Ben Carter

__________________
Ben Harrison Carter
1999 Mercedes ML320 87K
1992 Mercedes 300CE 89K
1995 Corvette 29K -- Sold Dec 09
1989 Mercedes 420SEL 99K -- (Sold 4/08)
1968 Mercedes 230S (106K) (Sold 9/06))
1976 Mercedes 450SEL 130K (Just sold - 06)
1961 Mercedes 220Sb (sold years ago)