Noticed this morning that the 12v receptacle on my 91 is coming apart. Need to figure out how to repair or replace. In the process of messing with it, the fuse blew (#1). Then I noticed that the windows wouldn't work (Fuses G and H), but those fuses were fine. Then when I replaced the #1 fuse the windows worked again.

Why does the circuit with Fuse #1 affect whether or not the windows work? Aren't they on different circuits?

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife

Fuse 1 controls the power window relay coil, that switches the power from G and H to the window system. The window power doesn't go through the key switch directly.

In fact if you look at your door jamb on the drivers side you will notice there's 2 plunger switches. One is for the dome light and the other is for the window relay. This allows you to operate the windows with the car off so long as the driver's door is open. This extra plunger switch pulls in that relay coil also. This comes from a different fuse than #1 that is not switched by the key. There is a diode block in the relay box that prevents mixing the two circuits together.

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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

Interesting....thanks. I wonder why that relay is not listed under #1 on the fuse map.

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14 E250 Bluetec 4Matic "Sinclair", Palladium Silver on Black, 157k miles
06 E320 CDI "Rutherford", Black on Tan, 175k mi, Stage 1 tune, tuned TCU
91 300D "Otis", Smoke Silver on Tan, 144k mi, wastegate conversion, ALDA delete

19 Honda CR-V EX 70k mi
Fourteen other MB's owned and sold
1961 Very Tolerant Wife