Honda-SOHC
SOHC.co.uk Forums => CB750 => Topic started by: MarkCR750 on September 13, 2014, 11:05:58 AM
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So far the headlight works high and low beam & sidelight, all 4 indicators work and all the idiot lights work except the oil light, the tail light also works, the stop lamp switches work, start button works and engine kill switch, but the horn and headlamp flash don't work, there are 2 wires from the nearside switchgear that I can't find a home for, one is blue/brown and the other is black, see picture below, does anyone know what these wires are for ?, also breaking out of the main loom next to the coils are 3 wires, the light and dark green wires have my original label from when I stripped the bike that says "horn" but the black wire doesn't have a label, it is live with the ignition on but I can't see what it should connect to?, any help would be greatly appreciated, cheers Mark.
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Thanks Oddjob, I suspect the combined horn flasher switch could be faulty, I'll check for power into it and then see if I can fix it.
The the black wire being a feed to the coils makes sense regarding where it breaks out of the loom but the engine runs so both coils are getting power without it being connected, the wiring has been messed about with in that area where the previous owner fitted electronic ignition so I'll have a look at where the power is being supplied from, thanks for your help.
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If your l/h switch has a PA/horn button similar to my 500 and 550 the horn works in a slightly different way, and the manuals usually only show the US version which does not have the PA, and just earths the horn wire. On the UK models there is a black wire to the switch in a plastic holder inside the bottom part of the l/h switch, this is the +feed for the horn and the headlamp flasher, when the horn button is pressed it sends the current through the light green wire to the horn, the other horn terminal should have a short wire to earth via the mounting bolt. When the PA is pushed sideways the current goes via the blue wire to the headlamp high beam as Bryan says in the headlamp via a 4 way connector. The little plastic holder can be dismantled and repaired with a bit of care. Hope this helps as there may be differences between different models. on my bike the black wire near the horn is not used, but would be on US market bikes.
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As said it sounds like you may have switch and loom from different years, brown blue MAY be for the later indicator buzzer but not sure.
Early bikes had horns powered and grounded at the switch whilst later ones were grounded at the horn and power came from the switch, likewise the starter circuit changed from grounding the solenoid at the bars to powering via the button although this was usually combined with the headlight permanently on but disconnected when starting
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Thanks for the input people, much appreciated as always.