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I did check that yesterday and didnt get continuity but i wasnt sure if there.we any.switches or other implications that would cause no signal.

To confirm with ignition off, dash removed and VR unplugged i should get continuity end.to end on the blue.from dash connector to VR?

geepeetee wrote: ↑Fri Aug 09, 2024 9:24 am To confirm with ignition off, dash removed and VR unplugged i should get continuity end.to end on the blue.from dash connector to VR?

Yes.

While you're at it, check all the VR wires for continuity.
If all the wires are good but the gen bulb only lights when grounding the blue wire, you have an internal fault in the regulator. This diagram should help.
I always have spare parts on hand so my very first test would be trying another regulator.

OK, at least you've made some progress. You've eliminated the supply to the bulb and the bulb holder.

I can confirm that the blue wires from the voltage regulator go 1) to the bulb and 2) to the diode board. It is unlikely that the wire to the diode board would have the effect you are seeing, even if it were open or short circuit (but it might be worthwhile disconnecting it at the diode board end to completely eliminate it).

With the connector removed from the voltage regulator and the ignition on, shorting the bue wire to ground should light the bulb. If it doesn't and given that you can get the bulb to light by shorting the negative side of the bulb holder, the strong implication is that there is a break in the connection from the bulb holder to the voltage regulator. Assuming that the voltage regulator connections are clean and sound, suspicion has to point to the physical wiring and connectors between the two. The answer to your question 'To confirm with ignition off, dash removed and VR unplugged i should get continuity end.to end on the blue.from dash connector to VR?' is yes... but the multimeter isn't the best tool to use to check this. It takes so little current that a bad connection will not necessarily show up. An old fashioned continuity lamp (or a 5 watt bulb with two wires attached) is better.

It's time to look at the blue wire in some detail... Being BMW, there are three arrangements for this blue wire. The earliest arrangement uses two seperate wires, one from the lamp to the diode board and the other from the diode board to the voltage regulator. As far as I can tell, this arrangement is used on /6 and earlier bikes but it's difficult to be sure because BMW had a habit of using up old looms so it could be fitted to early /7 machines. The second arrangement has the same two wires but physically connected in the same spade connector at the diode board. On the third arrangement, the wire from the lamp goes to the voltage ragulator where it is physically connected to the wire to the diode board. The point of this detail is that, with the third type, you can ignore the connection to the diode board (for now anyway) but on the other two, you will need to remove the diode board because the blue wire(s) connect(s) to the rear of the board.

Note... when removing the front cover, make sure you disconnect the battery otherwise you are likely to short out the diode board and destroy it...

Rob

Hi

Thanks for the advice, it's sorted.

I've found a badly corroded bullet connector in the blue wire from the VR to the gen light under the tank. Cut.out, soldered and.heat shrink. Charging like good un'.

Thanks again

Gary

Images before and after : )

That'll do it... I don't think that's a BMW connector, they usually used Lucar connectors like the other one on the images. Looks like some PO has had a problem there before...

Glad it's sorted

Rob