Pelican Parts Forums - Fuse #10 keeps popping

Came across this awhile back and saved it. Hope it helps.

Many E30 drivers with a manual shift end up with a sloppy shift after a few years and are surprised to find their backup light is gone (and so their sticker on inspection). Duh.

Worse: Some find that fuse 10 blows all the time.

What gives?

The cable connecting to the backup switch on the left side of the tranny (above the oil plug), returns on "close" plus 12v that it gets from fuse 10 via the C301 connector (Bentley sect 15, fig 10-10) inside the shift boot. C301a gets the 12V from fuse 10, then feeds that switched signal to the rear light harness under the carpet somewhere.

The two wires are coded Blue-White and Green-White. C301(a and b) is a dual white plug. Somehow BMW laid the not reinforced or doubly insulated wires from the tranny into the shifting boot between the metal housing and the rubber boot (where they get squished, the insulation gets cut open and the wires shorten against ground in a "shifty stick" or "wobbly shifting" tranny!), then the wires are fed through the boot, out a hole on the right, to end up in C301b which connects to to C301a, who's wires end up under the carpet (FROM fuse 10 and TO rear light harness).

This is sloppy engeneering.

Fix:

I ripped out the rubber boot, cut c301b off with enough to solder on a new pair of wires, blue for Blue-White and red for Green-White, made sure it wont short and will hold, and drilled a hole away from the rubber boot (the first was too close). Then I pulled the wires through, pulled up the wire from the tranny switch with an aluminum snare, and soldered the blue and red wires correctly colour coded and sleeved with heatshrink tubing on. Then I fed enough blue-red wire to give a little slack to the wire to the tranny switch, squished in a radio-shack grommet to make the entire thing hermetic , (remember: you can see the street through that hole) and Voila!