Welcolme......


The early ML uses a blend air system..no heater valve. Also no diagnostic abilities on that early system.

There are 4 possibilities for your problem..YOU will have a hard time trying to figure out which one will rectify the problem.

The in-car temp sensor
the control unit in dash
the blend air motor &
the blend air control unit.

ANY of those could cause an intermittent problem like you are having.

__________________
MERCEDES Benz Master Guild Technician (6 TIMES)
ASE Master Technician
Mercedes Benz Star Technician (2 times)
44 years foreign automotive repair
27 Years M.B. Shop foreman (dealer)
MB technical information Specialist (15 years)
190E 2.3 16V ITS SCCA race car (sold)
1986 190E 2.3 16V 2.5 (sold)
Retired Moderator