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-   -   Electrical issues solved ! (https://mercedesforum.com/forum/mercedes-benz-forum-help-suggestion-center-8/electrical-issues-solved-59981/)

Steveras Nov 7, 2019 01:00 PM

Electrical issues solved !
 
Hello again had to come back and tell the story of how i fixed the electrical issues i posted yesterday- its well weird i dont actually belive it myself bit ufo/loch ness monster/paranormal stuff.
After fitting a replacement center console switch unit no change, so re-visited all the stuff id checked before!
comfort relay (number 14 in engine bay fuse block) working -clicking when the ignition turned on so energising ok!.
checked again fuses 24 and 25 in the drivers footwell ! 11.98 volts at both as it should be!.
Re-checked green relay next to fuse,s 24&25( its not actually a relay just a bridging terminal no diodes or switching) voltage reading normal so not any of these things.
Took the center consol out again and checked voltage at pins one and seven as suggested found no power coming through which kinda stumped me as it implys that some thing id already checked was wrong ! either that or something real serious was wrong (suspect sam module or the like at mega expense) or huge bill at auto electricians trying to diagnose the problem, got a bit depressed at this point and went in for coffee &cake and decided to revisit the web to see if there was any information i might have missed.

On an obscure site somewhere (sorry i did not save it so i can't say exactly where) there was a guy who had had the exact same problem- his investigations lead him back to the engine bay fuse box where unbelievably he discovered that fuse number 31 WAS COMPLETELY MISSING!,he said/implied that it had never been installed in the first place !?.
Anyway having read this i popped the lid off the engine bay fuse box again- and found that the second row of fuse,s (29 to35) were missing/not installed at all ?
just on spec i decided to pop a fuse into location 31(mirror control) and see what happened (if anything!).
blow me the mirror switch,s now worked both folding and adjustment, couldn't believe it! so in shock tried the windows and all were working-what can i say?.
Dont know really but i can tell you this!
I CAN CATEGORICALLY STATE THAT TO MY KNOWLEDGE THERE NEVER WAS A FUSE FITTED IN LOCATION 31 (OR ANY OTHER LOCATION BETWEEN 29 AND 35.)
that row was ALWAYS empty!.
No idea why fitting a fuse in that signal location fixed the issue, and i must also say that even if i am wrong and there was a fuse in location 31 originally- then what happened to it to cause the problem is a complete unknown!.
If anyone out there has any idea why fitting a single fuse in a single location solved the problem i would be well interested to know, only thing that i can speculate is maybe popping a fuse into that location re-routed the signal through one of the s.a.m units in effect by-passing the original problem /failure point!
don't know just glad it,s working again but bugs me a bit that the fix is a bit" Heath Robinson" hey-ho at least it,s done.


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