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BobRoss78
03-04-2015, 11:04 PM
so i am by no means an electrician. im going for a very simple wiring setup on my '74 cb750 chop and have been using both the stock diagram from the shop manual as well as the basic diagram from hondachopper.com just kind of comparing back and forth.

the problem is the guy that owned this before me started, but never finished... so im unwrapping everything and sorting out his mistakes as well trying to see where he was going with it.

i think i have it most of the way, just a few odds and ends to tie up as well as getting a battery that works.


a few questions: both diagrams show three wires for the headlight and taillight. i have an old taillight off of a truck and a random taillight i got and both only have two wires coming out of them. obviously, one will be used for ground, the other to make the light work. im just trying to wrap my head around what wires go to what and which to delete out of the diagram with only having 2 total.


pics for reference:

twitch99xl
03-05-2015, 4:43 AM
hmm id bet those are internally grounded and both wires are power

Hotel
03-05-2015, 9:17 PM
Nice catch twitch. I don't know much about electricity and all that, I just sat down with a voltmeter and a OE wiring diagram and started from scratch until I got spark. (Lights not yet wired in) But I think twitch is right, one in constant and the other is illumination for brake probaly.
But none of that answers your question about eliminating the extras. Strip them, find out which ones are hot and play connect the dots for a bit until you get it to work. Like i've said, i'm by no means an electrician but wouldn't one only be hot when the brake handle/pedal is squeezed?

KingHerald
03-06-2015, 5:49 AM
Nice catch twitch. I don't know much about electricity and all that, I just sat down with a voltmeter and a OE wiring diagram and started from scratch until I got spark. (Lights not yet wired in) But I think twitch is right, one in constant and the other is illumination for brake probaly.
But none of that answers your question about eliminating the extras. Strip them, find out which ones are hot and play connect the dots for a bit until you get it to work. Like i've said, i'm by no means an electrician but wouldn't one only be hot when the brake handle/pedal is squeezed?

Yes, one wire is for the tail light, the next wire is for the brake light, and the third will be the ground. Depending how you lights and stuff are mounted you can eliminate the ground, as long as there is a good connection between stuff all the way to the frame, which is the main ground.

For example, you can't run it without a ground wire if you have a plastic fender.

Same with the headlight, one wire for high beam, one for low, maybe one for running light, and one for ground.

The way I've done a loom before is to draw the required components on a sheet of paper, and then work out exactly how much you really need in there to connect 'em up. Some wires seem to go back and forth for no good reason.

JRyan
03-06-2015, 1:16 PM
2 wire headlight is hi/low beam, grounded through the shell. 2 wire brake is run/stop, grounded throu the shell. which should work fine if theyre mounted to raw steel. i usually run an extra wire for ground to the light with a wire eye on it and mount it to the light mount just to be sure it gets a good ground. and its always easier to just rewire the whole loom than to try and figure out what somebody else was thinking. that way you know for sure that theres no flaws in the system that may send you chasing your tail later. if you do it from scratch, you know what you did, and how to fix it if something goes wrong.

Nimrod
03-06-2015, 3:29 PM
its always easier to just rewire the whole loom than to try and figure out what somebody else was thinking. that way you know for sure that theres no flaws in the system that may send you chasing your tail later. if you do it from scratch, you know what you did, and how to fix it if something goes wrong.

This. wire is cheap.

555
03-08-2015, 4:01 PM
Check the garage section at www.hondachopper.com
555

Sabai
03-08-2015, 6:03 PM
it's a running light wire, for when you flip the lights, unneeded unless you want blinkers on when the headlight is illuminated. Look up in the Wiring Diagrams sticky at the top of the page... we have some minimal up there that should guide you along.

A bike mechanic is many things electrician included... ;)

CarloFreeze
03-08-2015, 6:34 PM
The easiest way to figure out which wire is for which part of the bulb on any 2 filament light (headlight or tail light) is to take the shell of the light, assuming it is metal, and hold the shell against the negative terminal on a battery, then try connecting each wire of the light one at a time to the positive terminal. It will light up and you'll be able to tell which wire addresses the High and Low beam or in the case of the tail light, which wire is for the running light, and which one comes on with the brake light switch to light up the 2nd filament.

Mocnyang
03-08-2015, 7:36 PM
Did you get this sorted out???

BobRoss78
03-18-2015, 11:29 PM
thank you for all the replies guys. so as said before, the headlight only has 2 wires. placed the shell of the light on the negative terminal on the battery and tested both wires to positive. lights up with either wire (duh) but it seems to be the same strength of light instead of hi/lo. im pretty sure this light is an old truck light, but who knows....

my brake light bulb is blown, so no testing that one yet. but upon further inspection, the tail light is definitely not internally ground, it has a black wire that grounds to the frame or fender it's placed on. so that leaves only one wire for the tail light for sure. this could be a dumb question as well, but this is an old butler light made in england and i was planning on just replacing the white lens with a red one and using it as a brake light. will this one wire setup still work for running and brake lights?

Mucksavage
03-19-2015, 11:27 AM
It could be that they are the same strength of light, but if you are running with the tail light on and step on the brakes, then they are both on and give you the brighter stop light.

Mocnyang
03-20-2015, 8:36 PM
Can't use the taillight for running and brake lights as it sits. Are you 100% that the other wire is for the ground? It needs one of 2 things.

First you can get a dual filament socket where the bulb will need 2 filaments internally and the socket will have 2 wires coming out for the positive and one for ground.

Or you can just install a second socket and run 2 bulbs where they will each have a positive wire and a ground wire.

If the housing only had 1 port for the bulb to go through them a dual filament will be required.

With all this in mind might be easier to get a new light. If your dead set on using this your going to have to re-engineer it to work.

Mocnyang
03-20-2015, 8:38 PM
On the headlight I believe they are usually the same intensity. My 74 shovels the same way.

JetBlackII
03-22-2015, 10:26 AM
So basically... you want to run an old headlight as a tail light, and both wires out of the housing; burn one of the filaments inside the bulb for each wire... which would mean the housing is the ground connection.

Well that would mean, you can run one as a running light, and the other for when you press the brake activated through the rear brake switch...

easy enough, attach one of those fuckers to a constant on power source wire on the key switch wire, and the other through the brake switch positive power. If you don't plan on a constant on tail light... the pig tail the bastard into one, and run it through the rear brake light switch.

BobRoss78
03-24-2015, 10:06 PM
thanks for the replies guys.

jetblack, i got a new light and tested it tonight to confirm that the ground is not internal and there is only one wire for the light. im trying to comprehend what you are saying about burning one of the filaments inside the bulb for each wire? i definitely want a running light on at all times as im not running a headlight switch or anything so both will be on at all times.