I have searched threads about heater issues but have not found a vacuum circuit diagram or a component location chart/list. I would really appreciate any help in this direction. Oh, my issue is heater on full through the defrost no matter what.

Thanks for any help.

201 service disc?

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1986 300SDL, 211K,Dealership serviced its whole life
1991 190E 2.6(120k)
1983 300D(300k)
1977 300D(211k)

Where do I find "service disc?" I have a Haynes manual but it is really sketchy- almost useless. I did an internet search but couldn't find anything referenced that way.

Thanks again