The only way to do this is to open the door card and snake the wires and hoses out and back in with the conduit in place.

I had to do this on the 300TD, it revealed several frayed wires caused by poor choice of strand counts on M-Bs part.

I would carefully inspect the wire pack going to the door. It would not hurt to replace the vacuum hoses if they appear brittle as well.

__________________
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