Will do,Thanks!

Do you have the key in the second "on" position?

Posting pictures of what you're seeing and where you're testing would be helpful.

Yes sir, the tail light comes on in the second position but Im not getting power to the dash or headlamp in any position. Looking at the diagram the headlight is powered by the yellow via the blue through the switch. They also show the white and green and green red in the mix. I wish I check voltage at the harness through the plugs... Any other ways to trace it down?

By law, taillight runs off battery on the USA CT3. Completely different circuit. Engine has to be running to get AC power to the yellow coming out of the stator.

Yellow goes to Key Switch. Now here is where it can get confusing. With the key in the lights-on position 2, the yellow connects to a blue... or blue with white stripe (blue/white)... coming out of the switch.

Because in about 1970 the US required the taillight to stay on with engine off, there is also a blue coming out of the key switch that connects to brown with the key in position 2.

The headlight/dash light blue should be a blue/white but I seem to remember some bikes where both were solid blue. Difference between the blues is the Tail blue has battery power with key in position 2. The headlight blue out of the switch has no power with engine off and AC power with engine running. Or just use your meter to tell which blue connects to yellow in the switch.

From there, the blue goes to the handlebar hi-lo switch and directly to dash lights. Blue into the hi-low beam switch turns to green (low beam) or yellow (high beam and high beam warning light) at the headlight. Be aware there are two shades of green in the headlight bucket. Darker green is for the turn signals and sometimes easily confused. That's it for the headlight.

The Green, Green/red, and white you're talking about have nothing to do with the headlight.

Green and Green/Red both go into the key switch from the stator. When key is in position one (headlight off) green connects to the white coming out of the switch. This is the "daytime charging" circuit.

When key is in position two, then Green/Red is connected to the white coming out of the key switch. This is "nighttime charging". Everything is AC at this point.

White goes to rectifier (still AC). Rectifier is a diode that converts the AC to DC. Red is now DC power coming out of rectifier and goes to battery to charge it.

Some models have an extra wire (white) coming out of the stator that is not connected to anything... CT3 doesn't as far as I remember. If yours does, it's an optional higher output daytime charging wire.

Manuals in the tech library explain all this and wiring diagram has a legend that shows which wires connect to which in the different key positions.

That is an outstanding, detailed write up describing the entire charging system wiring. Thank you MarkT for taking the time to produce it, I will print it to keep near my electrical testing tools!

Yes! Thank you so much Mark! I tested the switch again blue white was dead pulled the switch and bingo! It must have got tugged off at some point after installation. Any advice for soldering it back on?

Great find! Easy fix if you know how to solder and have a soldering iron. Never use acid core solder on wiring. Use rosin core.

If you don't know how to solder, practice first. Probably lots of YouTube videos.

"That is an outstanding, detailed write up describing the entire charging system wiring. Thank you MarkT for taking the time to produce it, I will print it to keep near my electrical testing tools!"

You're not the only one hitting copy and paste....
Electricity...if I can't see it move, it's a mystery to me.

Thanks again Mark, I got it back on! Kinda surgical move to get in there. I’m a full time blacksmith so I’m familiar with putting metals together, not a big fan of soldering though....
Gonna give her a test ride this afternoon!

New to the forum

I have a 76 DT400C and had similar symptoms
This explination is super valuable and it looks similar to my DT so super thanks
My light and gauges are not on when running
I removed my magneto and removed lighting coil and put 6v to the yellow and the headlight came on and all is working like it should
ordered an NOS coil and it's on it's way.... (Argh forgot to check the speedo / tach lights when I had it hooked up)

Question: On the attached 

• Making sure all the A photos are the yellow as the colors are kind of discolored
• My eyes suck so I colorized a diagram (feel free to share if it's all correct)
  • If you know any other colors at the magneto let me know and i'll finish it
• I think I have only 2 coils, power and light so not sure why the diagam shows three coils?
• I have yet to test the green/red to see if charge works when running

My magnets were a bit rusty and the ends of the coil were pretty coated gummy too
Would it help to wire brush the ends and maybe clean them up or if the magnets work leave them be?

Any advice would be appreciated from all that know!
Cheers