Topic: K8 Neutral & Oil light not working. - SOLVED

[crispin]

I have a CB750 K8. I've searched many archives and can't exactly find help.

I bought a new speedo from DCC, replaced the original one on my bike. The new speedo I ordered has built in neutral light, oil light, etc... It still has seperate wiring for each light, so that's fine. The crazy thing is that my neutral and oil light doesn't work. It's crazy because I wired my old light's and speedo ON TOP of my new speedo's wires, and the neutral light works for my old indicator lights, but not the new speedo.

Yes, I have double checked, circuit tested the wires. I'm currently running through to make sure the diode, switches, and connectors are good, but so far, it seems good.

Even more crazy, as I'm turning the key to my ignition switch off, I see the neutral and oil light blink really quick. I don't understand. Does anybody have any light on this? (no pun-intended)

[crispin]

Also, yes, I have checked fuses, all is fine with those.

[HondaMan]

By chance...are the new lights LED type? If so, they might not light up because of the type of switch contacts these old bikes have. They are not "electronic" type contacts, plated with gold, silver, or palladium to ensure very low current (like 10mA) to light LEDs. This is a common trouble with aftermarket stuff...the contacts in these switches are zinc-plated, for the most part, so they have to 'break' current at about 50mA before they actually work.

Another item: check the grounds for the new instrument, and don't trust the handlebars or steering head to ground for you. Instead, run a ground wire from the one for the LEDs to the Green wire circuit on the bike somewhere (like in the headlight) to make it ground to the actual wiring.  The steering head only grounds thru the bearings: this is poor even for lightbulbs, so Honda was wise enough to include Green wire grounding throughout the bikes.

[KeithB]

Also, with LED lights, they only work wired one way so reverse the connection and see what happens.
Have you tested with an incandescent (regular) bulb to make sure everything is working?
Both these ccts work with power to the bulbs and then the switch makes the connection to chassis.

[crispin]

SOLVED!

Hondaman, they are LED, so thank you for bringing that to my attention. I found green wires for ground, but that didn't work.

KeithB, I reversed the connections, and everything works! It all checks out.

So weird, why would that be the case? Anyways, I've been trying to figure it out for a few days now, so thank you so much!

[madmtnmotors]

KeithB, I reversed the connections, and everything works! It all checks out.

So weird, why would that be the case?

LED = Light Emitting Diode

Diodes only pass current one direction thus polarity matters.