Headlight A/C, are you SURE?

Thread revival here … Actually got here from a Google search. So I am a Yamaha guy and have been helping a buddy of mine get his 2007 CRF450X squared away with a new Tusk dual sport wiring harness and a pre-existing K&S handlebar switch assembly. He just bought the bike and while the previous owner had a rear brake light switch installed, the only other real mod was high and low beam off the headlight. Not much of an existing DS harness.

After working through the Tusk harness to K&S switch wiring issues, I ended up with a dark blue wire off the K&S switch (for “parking light” or something) that didn’t appear to have been hooked up to anything in the first place, wasn’t even stripped, so I folded that wire up and shrink-tubed it. Putting it all back together, the brake, running, and turn signal lights all worked great, but no headlight at all with the bike running (I could have sworn headlight was on AC and only came on with the bike, though I didn’t take note of that before we started this job). With it all apart again, I measured AC volts at the headlight harness with bike running of course and got about 0.6 VAC. Wouldn’t register DC volts. As far as I know (my friend here had taken stuff apart when I wasn’t there to help), we did not mess with the existing headlight wiring with the K&S set up and it did work before. But it stopped working.

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Read more: Headlight wiring short. – Harley Davidson Forums

So after tearing it back apart, removing and opening up the switch assembly to check voltages in there, the only thing I could think of was that blue wire I had capped off. I tried running it to the hot positive up front that comes from the battery (where the Tusk kit has provisions for an on/off switch – which we are running in the form of a waterproof toggle switch to kill the other lights). As soon as I ran that wire to positive, the blue LED indicator on the K&S switch came on. Cool! I then hooked up the headlight, had him start the bike, and it worked like a charm, with headlight on/off capability on the slider switch and low/high beam with the push button switch.

What has me completely confused though, is now the headlight is running off DC for sure. I know this because you can turn the headlight on with the engine off. What did I do here and is it safe to run? Everything appeared fine – no popping fuses, no burning wires, no wild dim-bright-dim headlight with engine running, or anything abnormal. Except for one thing: his battery, a Ballistic lithium, is very low right now – 9.8 v (have to kick start for now). It doesn’t seem to be really charging right now when running, but I only checked running voltage at idle late tonight – did not run RPM up at all. We are going to go ride tomorrow, and will see if the battery takes a charge, but this DC headlight thing has me confused.

Long post here. Just want to check with the CRF gods on this – I have a suspicion that we’re exceeding some sort of electrical design limit with this now. Thanks for any help you guys can provide.

Read more: Harley-Davidson – Wikipedia

Source: https://tonupboys.com
Category: Headlights