Wiring issues

[jfrench]

Merry Christmas to all
i I had to re wire my head light plug on my 78 Gs 750
theres only 3 wires, I matched them up white, black and yellow. (If these are the right wires to begin with). I plugged in an H4 bulb and nothing happened. Does this need to be grounded in the headlight assembly before it with turn on
I checked voltage to the plug and I have power to the white, and yellow wires but not black thinking this is ground. Please help
thanks
jim

[rphillips]

Pretty sure Yellow- Hi beam, White Lo-beam, Black Ground.

[jfrench]

• Can you just plug in a bulb and turn on the ignition switch? I don't have the head light bucket or even a headlight attached like it should be.

[Big Block]

Absolutely.------

[rphillips]

Yes, If you have 12V to either the white or Yellow & the black "is for sure grounded" bulb will light... Be careful that bulb will instantly be suuuuper hot as soon as it lights... Just say'in, you have a "78" model? If so your headlight switch is there but shouldn't work (slide up & down) unless it's already been fixed. If it won't slide, and you wish it did, remove the little plastic slide button thing, trim the little stop tab off the bottom and re install. Should have an operating on off switch, just like the "77" models had.

[jfrench]

Thanks all, but one more question please. If I check the plug with a volt meter, and I have, I set the meter on volts, and check line voltage, what should it read? 12 volts? I get a reading on the white side and the yellow side on low beam and when I switch to high beam, the meter jumps to a higher reading. but the light still does not light up and these are brand new bulbs.
Thanks for all of the info

[rphillips]

Key on, switch on HI, should have 12V on yellow wire and nothing on white. Key on, switch on LO, should have 12V on white wire nothing on yellow... On your bike, when all working as new, You can but should never, play with the switch and get it half way between LO & HI and get 12V on both wires, both LO & HI beams on at same time. Will have a brighter light but will be producing almost double the heat it was designed to run safe with... As always, just my opinion.