Topic: really strange wiring issue....

[Geeto67]

So I did a stupid thing. Instead of selling my two F bikes like I have been promising to do for months now, I bought another CB750, a 73K this time. The bike is just ok, largely built out of parts at this point but it runs really well, and it was really really cheap.

riding it home the other night I noticed something odd about the electrics. Whenever I turn on the blinkers the headlight shuts off. WTF? At first I thought it was a short in the switch but the turn signal switch and headlight on-off switch are on opposite bar controls. The only other thing I could think was that it was the high/low headlight switch which appears to not be functioning and stuck on bright.

any ideas? I've seen a lot of weird shorts and such but this one is kinda weird to me.

[TwoTired]

Grounding issues?

[jdpas29]

i had the same problem.  it is a grounding issue.  there are some grounds to the blinkers if i recall that don't need to be attached to anything or something weird like that.

my headlight is still screwy.  i can't get the high beam to work by itself... it is always in combination with the low beam which you can imagine puts quite a tug on the battery.  since i hardly ever need my high beam anyway, i just don't care.  8D

[Bodi]

Something is fricked up with the connections for the switch pods. I would verify these first, that the wire colours all match for the connections. The high beam switch controls the front marker lights overall, and the signal switch controls them individually. So maybe there is something crossed up in there, does the headlight go off signalling left and right or just one way?

[Geeto67]

it goes off signalling left or right and does not favor one direction over the other. wiring is my weakest point on these bikes

[HITMAN]

Just thinking about this, is it possible it was hooked up to a running light (in the signals) circuit.  With several of my bikes that have running lights in the signals, the running light goes out when you turn the signal on.

Does the high beam do the same?

[Tower]

The problem is not obvious - it is related to the fuse holder.  At least it was on my K3.  i.e the ground connection was loose and somewhat corroded.  Remove the fuse holder and clean mounting connectors with a dilute acid solution such as a jellied rust remover.  Wash with water, dip in acetone to dry, and lightly apply an electrical grease.   Reattach holder to bike using new thin lock washers.

[jmckinne]

I'm having trouble with my headlight/running lights/swithc right now too. Here's what I've found:

1) The headlight power runs into both left and right hand switches. Power comes into the hi/lo switch and the position of the switch determines which output is engerized. Entirely possible for your whole problem to be in the left side.

2) There are LOTS of ways to short across circuits in there and for switch contacts to intertact. Open it up and look around for mechanical shorts etc. Mine had metal shavings in it for instance.

3) The way the wires clear the switch housing is stupid. The opening for the handlesbars is where they go out and the flange there is perfectly capable of gnawing its way thru insulation and causing a short or cross circuit. On mine, if I tighten my switch case screws beyond a certain point I cause a short and blow my HL and/or main switched accessory circuit. If I have the light switch in the off postion I don't get a short, but I also don't get lights.

4) I found a zillion little cuts in the insulation on my switch harness wires ao I just order a whole new LH switch. It comes with the wiring harness. Decided I wanted piece of mind, and hoping I found and taped all the little tiny insualtion cuts wasnt going to give me any.

Good luck.

[Jerry Rxman Griffin aka MuthaF'er]

I was having headlight problems recently but not a turn signal headlight. Quite novel but very ineffective I should add. My headlight just quit working. No problem - the fuse. Fuse good. Crap! Then it's gotta be the headlight bulb. Not. Has continuity. #$%*! Full power on both sides of the fuse. Dammit! Power at my junction box on the down tubes (75 750F). Geez F! Check the schematic. Time to open up BOTH switches as JMcKinne points out. Starter button plastic case inside switch housing on the right is jacked/cracked/broken. No wonder the friggen starter switch isn't working correctly. Hooked up the new switch at the junction box before pulling wires from the handlebars. WooHoo, it works. No headlight. F..k, now I gotta pull those friggen wires to get my starter button working once again. Done and hooked up. It starts. Headlight? Not. Gotta be that damn left hi/lo switch. The switch appeared to be separating at the top and the contacts perhaps coming apart?! Bridged the contacts with my screw driver blade. Full voltage, no #$%*!! So thats where that small funny shaped piece that I found on the tray of my work stool should have gone (to hold the switch together). What idiot left that off then got too lazy to check?!! Contact cleaner and dielectric grease. Reinstall PROPERLY this time. WooHoo. Headlight works high and low, UNTIL I move it. What the F...?? Can't be. Yes, it is! Looks like the bulb is kinda loose in the socket. No prob, I'll just bend the individual prongs on each wire. Maybe on 2 outta 3. #3 is cracked and doesn't allow proper pressure on the light bulb blade. Problem now solved. WHY COULDN'T IT HAVE BEEN THAT DAMN FUSE?? Just too easy I guess.

Moral: Pay attention to detail and don't overlook the obvious. Use a schematic and track down your wires. Be sure the wires are connected to one another correctly considering they are color coded. AND, put every thing back together properly the first time. Double check all the grounds. Make sure all the connectors provide proper tension when connected and are not broken.

It's going to be a simple thing when you find it and it's really going to piss you off. Have a beer!