Go to startekinfo.com or w124-zone.com
Find the link for the service manual
Chapter 83 explains it all.

Check fuse 7 first...that is the main power feed to the controls.
The blower is either Fuse 12 inside the box (early 87s) or in an external fuse holder just forward of the main fuse box.

But if you lost your main fuse 7 then you will have no action at all even on the blower since the controller can't tell the blower to start.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech