Blown fuses?

Last Saturday the bike quit on me w/ a blown fuse. Wiring under the tank was bad, loose bullet connections and I replaced all the bullets w/ crimped weathertight connectors. Bike started right up, and the lights were brighter. 5 miles into my ride today another blown fuse. What the hell! Replaced it and it blew immediately. Replaced it again and it ran almost home when it blew again. Time to systematically check each connection that I haven't already redone. The fuses look like they've been overheating slowly as they have a shredded copperlike appearance.

Could a Boyer micro mark3 possibly do this? Any suggestions or input appreciated. One other thing, each time it happened was after a plug chop using the kill switch. I've checked that and it appears ok. There's no voltage drop across it and it ohms out ok. Thanks, Rick

If one bullet connector was bad you have to assume ALL bullet connectors are bad. That means everywhere on the bike. Not sure how many you replaced, was it just the ones under the tank?

Sounds like more than dodgy bullet connectors. Lights got brighter? I'd suspect an earth is poor or there is some chaffed wire that's shorting. Is the harness old and decaying? Rip it out, spend $190 bucks and fit a new one if in doubt. Surest reason for sudden breakdown on a Commando is poor electrics.

Mick

My bike's favorite places for a short is where the wires for the rear brake light switch come out from behind the primary chain case.

Greg

Well I replaced the harness last year altho I confused the fuse (heh heh) rating and things got a little hot before I discovered the fuse confusion. Been running fine since then. The only bullets left are in the headlight shell. I did remove the assimilator and didn't connect the wires to anything. The bike has no turn signals, a podtronics reg/rect, Boyer so there's a lot of wires hanging around doing nothing. I'm considering rewiring for negative ground and doing my own harness w/just the wires I need. Something way simple and robust. Right now I remain disgusted w/ the electron gods. Time to walk away. Maybe this afternoon

Could the wiring to the charging circuit have got mixed up with the ignition circuit?

It sounds like the main feed from the battery may be wired straight to earth via the kill switch?

Difficult to diagnose at this distance

A less robust but more simple solution would be to stop doing plug chops :mrgreen:

rgrigutis said:

Well I replaced the harness last year altho I confused the fuse (heh heh) rating and things got a little hot before I discovered the fuse confusion. Been running fine since then. The only bullets left are in the headlight shell. I did remove the assimilator and didn't connect the wires to anything. The bike has no turn signals, a podtronics reg/rect, Boyer so there's a lot of wires hanging around doing nothing. I'm considering rewiring for negative ground and doing my own harness w/just the wires I need. Something way simple and robust. Right now I remain disgusted w/ the electron gods. Time to walk away. Maybe this afternoon

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Removing the assimalator would not be the culprit unless the connectors have not been taped up. Do you mean the fuse got hot? I am assuming that you fitted a fuse with a lower continuos rating than that specified. If you mean that some wires got hot this would imply that there was a problem and you could have wires that have literally melted together somewhere in the harness and the problem has only now revealed itself due to wear and tear in the harness.This could be time consuming to track down but with a half-decent multimeter and a wiring diagram you should be able to do it. Repacing the bullet connectors will not fix the problem as it is being caused by either the wiring harness or a component shorting out. Dodgy bullet connectors will just cause voltage drops across each circuit, so when you replaced some bullet connectors the headlight got brighter that was because the voltage drop across the connector was removed restoring 'full' voltage to the light. An intermittent faulty coil could be a problem if it is shorting out across the casing look at the Boyer wiring is any of it sort of wrinkled??

Many thanks for the replies. I was just out there taking off the seat and tank making ready to slice the harness wrap and see what's what. This immediately caught my eye
when I installed the harness a year a d a half ago I taped and tucked all the unused connections out of the way. This is the flasher feed come lose and straddling a frame member. I apparently put the seat on and plumped my bahumpas on and rubbed the insulation away on the 2 whites. Thanks again. Me'n the electron gods are good to go now. Rick

What is the proper readily available american fuse to use on my new harness?
I was hoping it came with the proper fuse. haha.
I now know 35 is NOT the proper amperage.
Some said 1/2 that, but what exact number do you guys use?
Thanks
Joe

Surf - I run a 25Amp (wire filament in glass tube) That is more than enough to protect the general harness and delicate contacts in the handlebar switches. Any higher and I reckon you could melt something expensive. You want a fuse to go instantly not pre-heat someting downstream.

Mick

Thanks ML,
I already did that.... in another thread there is the full sad story.
I got replys but everybopdy kinda beat around the bush instead of lighting it on fire. so to speak.
Like in my case. I blew the fuse the PO had in there somehow.
I replaced it with another of the same amperage: 35!
When I had a real short later the new fuse did not blow hence melted wiring harness.
Learned the hard way.
The new harness is due to arrive and I will go with a 20 or 25 amp fuse to start with.
Joe dog

A 20 Amp fuse is enough, in fact a 15A fuse should be adequate.