i was told that for liability reasons all mercedes climate control systems will always defaut to a heat mode during major component failure or total vacuum or power loss.

the example i was given was if you are in freezing temperatures and the system fails and cannot provide heat or the ability to clear the windshield etc.. the customer could be killed or injured in an accident. they could also freeze if the system is not providing heat.

on the other hand it was said that if you were in the desert and the system failed, no a/c but if the heat were on it would be uncomfortable but would not under normal cicumstances cause an unsafe of fatal condition.

this is what i was told, i have never actually seen it in print

so by unplugging the monovalve you are removing the power and it opens allowing coolant to enter the heater core

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1967 250 S
1967 280SE
1968 250S
1971 280 SE
1973 220
1974 280 S
1975 450 SEL
1976 220 D
1979 300SD
1983 300 SD
1985 230 TE euro
1986 280SL
1986 500 SEL euro
1986 190E 2.3
1990 300 SE
2003 C230 K
2004 C230 K
1987 560SEL
1987 300SDL now in canada
2005 C230
1998 C43 AMG Sold to DON
1993 190E 2.6
300TD Former daily driver Totaled
current:
R320 CDI
Ram 2500 Cummins