Bosch bewilderment?

[markQLD]

So, I was tracing through the wiring of an early 1970 750-S that was blowing fuses.
Reckon the problem was the terminations of the rear taillight, as not blown another fuse, as yet. But found a couple of other odd-bloody-wtf wiring terminations.  ???
The Bosch switch had a terminal, at the front of the board, connected to an earth bridge floating about in the shell. See attached pic with the highlighted yellow curve. I disconnected this black wire. There is also a brown wire from the top of the switch board that dangles down aimlessly lost?

My knowledge of this early BOSCH headlight switch is zero, nil, naught, zip.
So, is/was this connection good? bad? or ugly?  (dunno)  Everything correctly functions without these wires connected.

My searching found Lemon?s comments and photos of his wiring, but did not find any sketches with all the Bosch switch terminals explained.
  cheers

 

[Dellortoman]

Looks like the flux capacitor is missing.

If it all works, close the headlight up and forget about it. Might pay to get rid of redundant wires though. If one of them is live (or becomes live when you switch something on) it might be what's causing your blown fuses. Leaving redundant wires all over the place will also confuse you (or the next bloke) next time you delve into the wiring.

 

[LJ-2]

I had rear tail light fuse blowing all the time, turned out I needed a new rear rubber insulater/rubber boot .

Like this https://www.ebay.co.uk/itm/Fits-Ducati-Narrow-and-Wide-Case-Scrambler-RT-MK3-CEV-Tail-Light-Rubber-Boot-New/112747180017.

My wiring diagram is on here,can post again if req"d, Mark.

 

[Shajota]

So, I was tracing through the wiring of an early 1970 750-S that was blowing fuses.
Reckon the problem was the terminations of the rear taillight, as not blown another fuse, as yet. But found a couple of other odd-bloody-wtf wiring terminations.  ???
The Bosch switch had a terminal, at the front of the board, connected to an earth bridge floating about in the shell. See attached pic with the highlighted yellow curve. I disconnected this black wire. There is also a brown wire from the top of the switch board that dangles down aimlessly lost?

My knowledge of this early BOSCH headlight switch is zero, nil, naught, zip.
So, is/was this connection good? bad? or ugly?  (dunno)  Everything correctly functions without these wires connected.

My searching found Lemon?s comments and photos of his wiring, but did not find any sketches with all the Bosch switch terminals explained.
  cheers

Hi Mark. I know jack about any of this, but when I was sorting out the wiring on the AE some of the connections didn't make sense including I think some issues because someone had done something with that terminal you are pointing out. After matching up the Bosch numbers had everything working so think it is now right.
EDIT - Ok let's try that again. The terminal you have highlighted should be numbered 56 on the ignition plate (although a bastard to see). It connects to high beam indicator light and tail light (I think). The brown wire coming from the top (mine was white) is also connected to your highlighted terminal & connects direct to terminal 56b on headlight bulb holder. (Will make more sense when you see the numbers on the components)
It appears that someone has wired in some different terminals and done away with the direct connection from 56b so probably all fine although interesting you had some doubts about tail light!!
I edited this after having a look at the wiring diagram - shouldn't shoot from the hip with a dodgy memory :-[
Obviously mine is a slightly different model so ignore all that if incorrect...??.. :-[
(Hope at least some of that makes sense)

 

[Tippie]

I'm pretty sure that the wiring diagram on Laverdamania is for that switch setup.
The tail light is on the parking light/meter lamps (illumination) circuit, the high beam warning light is an add-on to the high beam wire to the main headlight globe.

 

[markQLD]

Thanks blokes,

I had rear tail light fuse blowing all the time, turned out I needed a new rear rubber insulater/rubber boot .
My wiring diagram is on here,can post again if req"d, Mark.

I've looked at your wiring diagram with your gang of relays, & noted the main switch shows no earth wire.
This 750-S has no fuse feeding for the stop-light globe. Feeds direct from front and rear brake switches. The fault (I reckon) was brake switches were connected to taillight reflector earth, and earth wire to stop-globe.
There is only two fuses. One fuse for all functions, and a fuse has been used to connect the battery to the voltage regulator. Odd but ok.

The terminal you have highlighted should be numbered 56 on the ignition plate (although a bastard to see). It connects to high beam indicator light and tail light (I think).

My test-light check showed no power to the inside terminal with the switch in any position. However, I didn't use both the high-low beam switch positions. The 'traffic beam' lights and 'town lights' are fed from other terminals. The terminal post next to it, on the front left corner, is for the parking 'town light'?

It just seems odd to have an earth wire connected to an insulated terminal post on that board. Maybe just a DPO thought-bubble? Maybe keeps the smoke in  :-\

.. and will take a squiz over at Laverdamania, thanks Lee.
<<edit> yep, it's the same as what I nicked off the Green Book >

, to be continued
  cheers

 

[Shajota]

Thanks blokes,I've looked at your wiring diagram with your gang of relays, & noted the main switch shows no earth wire.
This 750-S has no fuse feeding for the stop-light globe. Feeds direct from front and rear brake switches. The fault (I reckon) was brake switches were connected to taillight reflector earth, and earth wire to stop-globe.
There is only two fuses. One fuse for all functions, and a fuse has been used to connect the battery to the voltage regulator. Odd but ok.
My test-light check showed no power to the inside terminal with the switch in any position. However, I didn't use both the high-low beam switch positions. The 'traffic beam' lights and 'town lights' are fed from other terminals. The terminal post next to it, on the front left corner, is for the parking 'town light'?

It just seems odd to have an earth wire connected to an insulated terminal post on that board. Maybe just a DPO thought-bubble? Maybe keeps the smoke in  :-\

.. and will take a squiz over at Laverdamania, thanks Lee.
<<edit> yep, it's the same as what I nicked off the Green Book >

, to be continued
  cheers

Yeh, I think that terminal causes a fair bit of confusion. (mine had some tell tale burn marks from wrong wires no doubt being connected at one stage)
If you connect your test light to a live feed on say your lights and connect other end to your highlighted terminal or brown wire all will be revealed. (When I edited my last post I deleted more than I meant) I imagine that whoever changed the wiring just used an earth from elsewhere.
If you inspect the numbers on the ignition plate and bulb holder it will clearly show they were originally a direct connect for your brown wire- (56b) (with terminal (insulated) also used for high beam indicator and I think tail light)
Anyway, I think I'm confusing myself, no doubt you will work it out...??????...

 

[piranha-bro2]

Mamma mia! No way I could tolerate a wiring system that looked like that! Wires inside headlights? No grazie!

Good luck - looks way way more complicated than it needs to be (to me) to operate the essentials on an SF!! So glad they redesigned it for my SF1.

 

[sweetas]

Its only got one Hooter !    Cant have enough Hooters...?.

 

[Dellortoman]

Looks terminal to me.

 

[Tippie]

Would have been done by someone from Britbike background, or had a big roll of black wire to use up.
Nothing wrong in keeping it nice and dry in a big deep headlight though if it doesn't need to be jammed in. It looks like it was originally done pretty neatly to me.

 

[markQLD]

.. If you inspect the numbers on the ignition plate and bulb holder it will clearly show ..

Enlightenment!    Grazie mille Peter
The key to unlocking my self-induced mystery was inspecting the numbers. d'oh!  :-X

Numbers were found on the switch plate and matched with numbers shown on the factory wiring diagram and also Lemon's main switch icon.
They were all there (30/51) (56) (58) (15/54) (31) (HO) (2)  and bulb holder (56a) (58) (56b) (31)  All elementary for an enlightened one eh.

The terminal in question was #31, and is indeed the earth for all the globes within the headlight shell. This bike has had other earth wires installed, however I reconnected #31 back down to the earth bridge.
To be sure, to be sure.

.. and then I discovered one or two other bloody bodgies. ffs!!  >

 

[LJ-2]

Glad you are getting there Mark, tbh I forgot all about those numbers! Well pointed out Peter.

 

[Shajota]

Enlightenment!    Grazie mille Peter
The key to unlocking my self-induced mystery was inspecting the numbers. d'oh!  :-X

Numbers were found on the switch plate and matched with numbers shown on the factory wiring diagram and also Lemon's main switch icon.
They were all there (30/51) (56) (58) (15/54) (31) (HO) (2)  and bulb holder (56a) (58) (56b) (31)  All elementary for an enlightened one eh.

The terminal in question was #31, and is indeed the earth for all the globes within the headlight shell. This bike has had other earth wires installed, however I reconnected #31 back down to the earth bridge.
To be sure, to be sure.

.. and then I discovered one or two other bloody bodgies. ffs!!  >

I knew once you worked out the number system it would all become quite simple...????. (I was just rambling off the top of my head, sorry to confuse)
BTW - meant to add, if you're blowing fuses, worth checking the wiring to the Gen / Neutral light. If they are wired reverse (?), lights will still work, however vibration will cause the bulb holder to short and blow the main fuse...?.(another live and learn :-[)