Headlight ground

1975 Mk3 headlight ground? I'm confused as to where the headlight and pilot light ground. There are copper ground sockets on the headlight bulb holder and the pilot bulb holder. There is also one copper ground socket on the headlight shell. The wiring diagram shows the ground to the pilot, tach, and speedo go to the headlight shell. Diagram shows the headlamp bulb as ground to earth? If I wire it so the headlight, tach and speedo go to the red wire in the main harness and the pilot only goes to the shell, will that work? It is positive ground. There is no way to hook up 3 wires into the pilot to ground to the shell.

'Ground' is harness red. Headlamp "Case Earth" on the wiring diagram is incorrect so connect the headlamp and pilot to harness red.

Note that the shell connection is so the front direction indicators have a connection to harness red (a bare-ended harness red wire with a brass sleeve bullet), it is not an actual 'ground'.
Your (BPF?) headlamp socket might be different to the (H4) type plug, below, however, the same applies.

So I will have five ground wires; from the tach, speedo, pilot, headlight, AND headlight shell all connecting to the one red wire in the main harness? The headlight shell will then be the ground for the direction indicators?

sadolfsonmark3 said:

So I will have five ground wires; from the tach, speedo, pilot, headlight, AND headlight shell all connecting to the one red wire in the main harness?

Click to expand...

There should be more than one red wire?

sadolfsonmark3 said:

The headlight shell will then be the ground for the direction indicators?

Click to expand...

The red wire with the bare end is the direction indicator 'ground' and not the actual shell, therefore, ultimately everything connects to harness red but it shouldn't be the only red in the headlamp harness section.

The shell terminal is there so the direction indicators have a connection to red as the shell and brackets are effectively rubber-mounted because the bracket tubes are sandwiched between O-rings at the top and bottom although there is likely to be some metal-to-metal contact, the headlamp assembly should not be regarded as a 'ground'.

If the headlamp is the BPF type then the pilot ground can be added to the headlamp solderless bullet...
...so that's one less wire to connect to harness red.

I received my new headlight and have connected all the grounds the way described above but am faced with another confusing dilemma. Put in a new ignition switch and things started looking up as things began to work. And then came the problems!
According to all the wiring diagrams I have consulted, The left hand switch should have a blue(U) blue-red(UR) and blue-white(UW) wire for the HL lo-hi(Dip-Flash??). On my bike I have a UR, UW, and UY wire coming from the LH switch plus another UW wire in the 6 pin connector.The diagrams show the UR going to the headlight and a U from LH and a U from the RH connected together. All the switches are original and function properly. I tried attaching the the UY from the LH to the U from the RH switch. The UR and UW wires went to the Headlight. When I turned the RH switch to Head and the LH to Hi the light came on and the Hi beam indicator light went on. When turned to Lo it went out. When the RH was to Pilot and LH to Hi or Lo there was no light. Changing any of these connections has resulted in heat so I dare not try anything else or smoke will follow.
According to the manual: "

1. The dip-switch is energised by the blue wire. This wire feeds from the light selection switch on the right handlebar. The blue wire receives power when the left side switch is in headlamp position (UP). In "Hi-beam" position the left s i d e switch connects the blue & the blue/white wire.This illuminates the main (high) filament of the head bulb. In "LO" beam position the switch connects the blue to the blue/red wire. This lights the dip or low beam filament in t h e h e a d l a m p b u l b . The blue wire is only live in position 4 (IGN and LIGHTS) of the master switch, with the selector on "head" (up).

Doesn't this indicates that the UR & UW wires are both connected to the U wire from the RH switch?!? It's also apparent the wires from the LH switched not wired per the manual ( U wire from LH to U wire from RH) seeings how there is no U wire from my LH sw. Can anyone please explain how to connect all of the UW, UR,UY, and U wires in the headlight shell and where they route? I'm not he best at electronics to begin with and now I am totally flummoxed. I appreciate any help!

As you have noticed the LH switch cluster does in fact have two UW wires. One connects to the dip (HI-Lo) switch and the other UW to the headlap flasher (horn button when pushed upwards). The two UW wires don't (usually?) join as shown on the factory diagram (marked with the 'X') so both UW wires from the multi-pin plugs connect to headlamp main beam.

sadolfsonmark3 said:

Doesn't this indicates that the UR & UW wires are connected to the U wire from the RH switch?!? It's also apparent the wires from the LH switched not wired per the manual ( U wire from LH to U wire from RH) seeings how there is no U wire from the LH. Can anyone please explain how to connect all of the UW, UR,UY, and U wires in the headlight shell and where they route?

Click to expand...

You will probably find 'U' connects to UY at the multi-pin plug so its UY from the plug to the RH Edit: Correction: LH switch cluster, not 'U'.

Thus:
UY from IGN.Sw. T4 to the RH cluster.
Then, U from the RH cluster to the LH cluster pin plug.
Then UY again to the LH cluster.

Note correction to my previous message. = LH, not RH.

So I connect the two UW wires from LH to one side of the headlight socket and the UR wire to the other side, correct? And UY from LH Hi-Lo switch to U from RH?

sadolfsonmark3 said:

So I connect the two UW wires from LH to one side of the headlight socket and the UR wire to the other side, correct?

Click to expand...

Yes (or the two UW into a double common connector along with the main beam wire and main beam warning UW).

Thanks LAB! I'll try it this weekend.