New harness blowing fuse

I put a brand new main wiring harness on my 72 Combat, back of the headlight and switch gear harness.

Hooked up battery and went to put in fuse and it blew.

Double checked all wiring connectings and confirmed color match up at front harness on wiring diagram.

Blew again.

Disconnected all connections to front harness, main switch, horn, rectifier, rear brake switch, assimilator, capacitor.
Didn't but probablly should have disconnecetd alternator and Zener Diode.

Fuse blows as soon as I put it in.

Is it possible that some fault is in the Zener or alternator that is causing this?

Any suggestions on what I should try? The harness is disconnecetd from almost everything and still acts like there is a short.

Thanks
Bob

Sure, with the key off and a 12 volt light put in place of the fuse hook or unhook one wire at a time till you light or un-light the bulb depending on what direction your working in. The Zenor is a good starting point.

Bad ground?

This isn't about the problem, but one that might come about with a new harness - in three seperate recent occassions, I had the fuse terminal inside the plastic holder fall off the wire! It was a crappy little piece of tin plate. Don't rely on it. Get a decent chunk of copper on there and good penetrating solder.

Where do they make this rubbish?

Mick

I'm really stumped on this one.

Right now the harness is hanging there totally disconnected at all points including main switch except the red grounding wires connected to the positive battery terminal and the fused wire connected to the negative terminal. No loose ends touching others or the frame.
When I put the fuse in the holder it still blows!

I even took my old crapped out harness and hooked it up the way the new one is, just to the battery and its fuse stays ok.

Although the harness is one I got on e-bay from someone who said it was new from a project he abandoned and it appears unused I'm thinking there somehow is a short within the harness itself.

Unless there is a solution short of ripping it apart I'm thinking I should get another harness.

Any suggestions before I give up?

Thanks for the advice previously offered.

Bob

Get a bulb from a blinker and make a tool by soldering a wire on the brass base of the bulb and one to the solder dot at the end of the bulb. Get some small alligator clip for the other ends of the wires. Now clip the wire onto the fuse contact ends so a bulb is the fuse it will light no blow. Make the light go out with the key off. Stop blowing fuses.

There is a problem with the harness. You will have to untape it by sections and use an ohm meter or test bulb with battery and start comparing wire connections in the harness with the diagram to find the incorrect connection. Sounds like a white is connected to a brn/blue somewhere.

I would get a new harness, there seems to be a short circuit between the battery feed wire and earth system. Are you sure that there is not a red wire connected to another colour at a block connector somewhere?

I am just fitting a loom to my 1972 Roadster and I note that the brown and blue negative battery power wire connects to the rectifier (which could be faulty if connected), the Zenner diode (which could be faulty if connected) and the power take off/charging port - in my loom this is just a disconnected wire with a bare end which could earth on something if you are not careful. Make sure that this brown and blue wire is completely disconnected from everything on the bike and if there is still an internal short, either cut the loom tape and have a look or replace it.

Tonight I'll start opening up the harness and look for the short.
I'll post what I find.
Bob

I would not open up the harness. You have purchased a defective piece of merchandise.
Return it immediately to the seller for full credit, also ask your shipping cost to be reimbursed.
If you open it up, it will no longer be "new" and seller may not take it back.

Subsequent to my last post, have you checked that the red and brown/green wires for the power/charging port are not touching each other at their ends? Highdesert is absolutely right in principle, however all of this would probably take a lot of time and effort, for a low priced component, that could otherwise be spent actually getting the bike going. I would open up the harness. It has to be an earth wire shorting to the power wire somewhere and once you find it repair it and tape it up with electrical tape, you will be able to fit it back on the bike immediately and get the project moving.