I am trying to troubleshoot the climate control system in my 1979 300D. The car has 188K miles on it and has worked flawlessly until it stopped. I am suspecting the climate control amplifier but would like to test components of the system prior to just purchasing new parts and installing them. Does anyone have a test approach that would help isolate the problems I am experiencing? Thanks in advance.

What kind of issue are you having? No regulated heat? No fan? No flap control? That year has the unreliable servo unit.

try here-

Mercedes Benz 107 SL SLC Heat AC Climate Control Troubleshooting

it's the same system in both cars. good luck, chuck.

Hi Paul,

Pretty much no regulated heat. I replaced the blower motor which was seized and now have heat through the defrost setting, but no high or low heat. I know the servo and the blower motor are working. I am suspecting the push button control may be next on my hit list but just thought I would try to get some direction before I wade into that.

The factory info gave no clues? Pity, always helped me. There is no silver bullet for this system. Good luck, chuck.