79 CB400 possible wiring issue.

[ShaunB]

I'm having some issues with the lights on my bike. All 4 of my turn signals work but only my front left marker works 100% of the time, my front left works 50% of the time, and the back markers won't turn on at all. The bulbs themselves are all fine. Also, my brake light will only illuminate when I'm on the breaks but remains off when riding. My head lamp won't light up either.

[Morbo the Destroyer]

All 4 of my turn signals work but only my front left marker works 100% of the time, my front left works 50% of the time, and the back markers won't turn on at all.

Are you sure you're supposed to have "marker" lights at all? Most bikes don't use the turn signal bulbs for anything but turn signals. Maybe your blinker unit is flakey and lighting the signals when they're supposed to be off.

Also, my brake light will only illuminate when I'm on the breaks but remains off when riding.
That's the way it's supposed to work. There should be a TAIL light that's on all the time, but it's either a different bulb or a two-element bulb (like an 1157). Replace the bulb or get the meter out again.

My head lamp won't light up either
Get the meter out and remove the connector from the headlamp bulb. Ground one lead and start touching the other to the 3 points on the connector. One is ground, one is high beam, one is low beam. If you have around 12Vdc on two of the pionts, your bulb is bad. If you don't, check your fuse box and connections.

[acecycleins]

There are like six to eight actual working wires in those old harnesses- right?- lol. Time to bone up on harness 101. Just get the colors down and make new ones. Should take about two days if it involves beers.

[Easy Rider 2]

Originally Posted by ShaunB

All 4 of my turn signals work but only my front left marker works 100% of the time, my front left works 50% of the time, and the back markers won't turn on at all.

First, there are no "marker" lights on the back, as indicated by those bulbs being single filament ones......with only one center contact point instead of two.

On a bike that age, there are two likely problems:
Loose or corroded sockets.
Bad grounds.

It is also possible, I guess, that some locations have the wrong bulbs in them but they are supposed to be keyed differently so you can't do that (easily).

And, lastly, how do you know for sure the bulbs are good ? The filaments inside can be intermittant.......although that's kind of unusual.

[xuan1982]

Originally Posted by ShaunB

I'm having some issues with the lights on my bike. All 4 of my turn signals work but only my front left marker works 100% of the time, my front left works 50% of the time, and the back markers won't turn on at all. The bulbs themselves are all fine. Also, my brake light will only illuminate when I'm on the breaks but remains off when riding. My head lamp won't light up either.

ok, no.. 80% broken,
try to buy another one.

[mscuddy]

Take off the gascap and screw it on a '71 CB350. Get rid of the CM400. What a load. That or paint it all over in silver rattlecan, like Billy Pilgrim's boots....

[Captain Steve]

CB400F wiring diagram « honda CB400F

Doesn't seem very complicated, just check your connections and the condition of the wires. After 32 years who knows what's worn away under there.

[ShaunB]

Wow, completely forgot where I posted this.

Thanks for the replies guys. Turns out I made some real newbie assumptions and all I had were some bad bulbs and loose grounds. ~head desk~