Another /6 electrical Gremlin

[splinelube]

Need some advice here. Bike is a 76 90S. just replaced the diode board with an Omega and all the wiring that goes with it. The bike starts well, and all the following work: turn sigs., head & parking light, rear lights, brake lights with hand and foot levers, horn works, lights in speedometer work-tach light has not workrd for a few years. So what is the problem -the idiot lights do not work. This week I pulled apart the head light to replace the reflector after the work I rechecked the idiot lights and they worked, installed the headlight and idiot lights gone again. I have replaced the starter relay., cleaned the ground wires to military shine at the left coil, replaced the fuses. Have not removed the instrument light harness because it has never been touched and the speedometer lights work. Any ideas. I believe the idiot lights and the rear brake lights are on the same fuse and the brake lights work. Any insight is really appreciated. Thanks

[Bobmws]

Look where you were last. Try pulling the headlight and check the lights again. It's pretty tight in there, you may have disconnected something when reinstalling the headlight assembly.

[bprigge]

Sport Tourer,

My 76 R75/6 had no idiot lights when I bought it last year. The problem was the printed circuit, if you don't mind me calling it that, inside the speedo/tach
assembly. The connections where the external plug hooks up where oxidized
on the printed circuit itself. I scrapped the insulation off of the foil right next to the plug connections and ran a solder bridge from the foil to the plug pins.
My tach ligh was out also. That was a break in the foil where the tach light plugs in. I also repaired it with a solder bridge. I understand that you can still buy the printed circuit from BMW for not to much money. Bruce

[flash412]

Do you have access to a wiring diagram?

Normally, idiot lights share a common hot wire and send the voltage to various sensors that provide a ground when the light should illuminate. The fact that all the idjit lites fail at once says you should look at their COMMON point, which in this case is probably +12V.

If you don't have a wiring diagram, I can probably find one and tell you what color wire to look for.

Start at the printed circuit board and work your way back toward the battery, looking for +12V. Sooner or later you'll find the break or disconnect.

[splinelube]

Flash I have two count them two wiring diagrams-Clymer and Haynes-neither is in color. I thought all grounds were brown or maybe vice versa all brown wires are grould wires, guess the latter is correct. If you could tell me the wire color that would be a real help. Thanks - Russ

[flash412]

Flash I have two count them two wiring diagrams-Clymer and Haynes-neither is in color. I thought all grounds were brown or maybe vice versa all brown wires are grould wires, guess the latter is correct. If you could tell me the wire color that would be a real help. Thanks - RussGenerally, battery-hot wires are red, switched-hot wires are green (often with a color trace), lighting-hot wires have different colors for headlight, highbeam and parking lights. I don't recall offhand what the defined color is for idjit light common hot.

Yes, brown wires are GROUND wires. But a wire that goes from, say, your idjit light down to the neutral switch (to ground) or oil pressure switch (to ground) is not a GROUND wire. It is a signal wire with a defined color and trace color.

Monochrome wiring diagrams usually have color codes or descriptions if you look carefully and patiently.

When I get home tonight, I'll see if I can pull the manual for your bike and try to noodle out what color(s) wire(s) you should look for and where to look for breaks.

[flash412]

MAN that is a sorry schematic for these eyes. Near as I can tell, your idjit light peecee board has a connector. Pin 3 of that connector supplies hot to a handful of the idjit lights. Your turn signal idjit light is unrelated to that hot. So is the high bean. But tach and speedo illumination ARE related, on the peecee board. Anyway, pin 3 has a gray wire with a black trace connected to it via the connector. Make SURE you have 12V at pin 3 of the connector. Work which ever way you need to in order to locate the problem.

Is your tail light messed up, too? They share the same fuse AND the same circuit. The clock and voltmeter illumination are also on the same fuse, but not the same circuit. Front parking light is on the same fuse, different circuit, too.

[splinelube]

Flash thanks for the info. Will get to work this weekend hopefully will have some good news to post afterward.