Oh boy. Fuse 5 powers a lot of things. Many of the are very important.

Unfortunately the rheostat has nothing to do with that circuit.

Brake lights
Reverse lights
Gauges
Cruise control
Trigger for the warning buzzer relay

were the loads on fuse 5 I found in 5 minutes of searching the diagrams.

Given your past history I would be looking at your rear brake lights. Didn't we have a problem back there before that I helped you with?

__________________
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