89' 560SEL, 92' 300CE
Aloha to all... my brother just bought a 1980 300D and he recalls having the defroster on once and it got hot. A few days later, (after the cold front went thru)  he can't get the heater to work. The blowers are working and all, but it doesn't get hot(not even the defroster now). Fuses all look good, he say coolant and stuff is all good. What else can I tell him to check?? Any help would be appreciated. He don't have access to the forum right now and we're 4000 miles apart.