Sorting through a PO's electrical "innovations"

So I dove into my headlight bucket's wire nest to wire in my new gauges and I've been trying to figure out exactly what the PO was thinking when they snipped and spliced in the headlight in a new and exciting way. (I've also been going through and soldering connections where he twisted & taped :roll: )

Background info: my high beam/low beam switch has never done anything.

From what I can decipher from my wiring diagram it looks like he spliced the headlight lead(green) into the ignition run/off switch coming from the right handlebar. There is also a 15A inline fuse here. This explains why my headlight turns on with just the key and not a running engine. However the third wire(yellow) coming off the headlight plug is not connected to anything.


There is another white plastic plug which is not connected to anything. It has two yellow wires coming into it, one leads to the left handlebar switches(dimmer switch I assume), and the other end goes towards the back of the bike somewhere. The black and green wires coming out of this plug have also been snipped. I can see the other end of the snipped green wire going to the dimmer switch.


Here is looking into the end of the headlight plug. It's a little melted from heat obviously. Was there originally a section of wire going from this black plug to the white plug in the previous image?


My main question I have for anyone is how I can wire this up so that I have high beam/ low beam again. I don't care if it goes back to stock or if I can make it work from what I already have, However my suspicion is that the PO wired it this way to bypass a possibly faulty headlight relay.

 

Yes. The headlight connector itself is part of a short lead that plugs into the white connector you're asking about.

 

I see several issues here ...

Firstly those connectors are designed to carry in excess of their rated current without melting, otherwise you'd have bikes spontaneously combusting right off the production line! So if you have a melted connector it is a sure sign of a "hot joint" or a mechanical connection that has a high electrical resistance.

Melted connectors usually result from corrosion on the terminals or the crimped joint to the wire which raises the resistance and turns them into mini heating elements, melting the plastic surround. Test the resistance of the headlight, then the circuit leg with it connected in series, they should measure to within a couple of ohms of each other. If not the wiring is imposing a high resistance and that's probably going to be at the connectors.

Next issue is how maintainable do you want the bike to be? I would be returning the wiring to stock throughout and making that reliable first, at least you have a circuit diagram for how that was done, you do have the factory manuals right? Print out the wiring diagram and check each leg.

Last of all the problem might be anywhere in the switching circuit, the power circuit or the ground circuit, all of which have to be checked and made reliable in a methodical manner or you'll be back at it in a week. Corroded switches are notorious for this sort of problem so check it by disconnecting it and measuring the resistance at the connector with the switch open and closed. It should be infinite open and almost zero closed. Any higher and you have a fault in the switch circuit.

Good luck.

 

I tried wiring the headlight back together in the stock configuration by clipping off the white plug and wiring the yellows to yellow, green to green, and black to ground. That gave me no headlight whatsoever.

I'll also add that the backlights on my gauges never worked on the stock gauges, nor the new ones I just put on. This leads me to believe that my headlight relay is bad, since on my wiring diagram it looks like the gauge lights pass through it as well. I saw another thread where someone cleaned out the connectors and this relay and it started working again, so I will try this first.

If this doesn't work, does anyone know if there is an aftermarket relay that could work in this situation, other than the one Len has for $75?

 

Test your relay by taking it out and jumpering the coil side to the battery, it should click. You can also measure the resistance, a burned out relay will have infinite resistance (ie. open circuit) on the coil side. A good relay will be a few ohms.

If the relay is ok you need to be sure you are getting power to it when you operate the switch, by tracing the circuits one leg at a time. Don't start buying and replacing parts till you find where the fault is or you are just wasting time and money.

You also need to be sure you don't need the engine running for the light to come on.