Electrical Disaster

Yesterday, fortunately while close to home, my engine suddenly quit. My first thought was that I forgot to open the petcock but a quick glance showed it was on. Then I saw a thick white acrid smoke pouring out from behind the battery cover. I quickly pulled off the cover and confronted a bundle of melted wires engulfed in a small flame! I was able to blow out the fire (thank god I had gotten a handle on my oil leaks a few weeks before, installing a small catch bottle in the oil tank breather, so there was noting else to burn. A couple of weeks ago I'm sure the entire bike would have gone up in flames).

Okay, here's what happened. It was entirely my fault. . . though with a little help from whoever decided it was a good idea to go against the rest of the world and engineer a positive ground electrical system. A few months ago I installed a battery tender, wiring up the pig-tail that allows you to plug it in easily. The plug has a bare negative terminal, but also a rubber cap that covers it. Apparently, the cap worked its way off, made contact with the (positive) frame and created a dead short.

Wires in the main harness as far forward as mid top tube are melted, but so far as I can tell only the ground wires are toast. None of the fuses blew, either the main one, or the small 7.5 amp one in the pig-tail. I guess that's logical since the pig-tail was connected directly to the battery and the short was direct from the negative wire through the frame (and red ground wires) back to the battery.

So, the big question is were any electronics damaged? The engine did quit, but I'm not sure if it's because the Boyer is fried, or because a wire melted through. The bike still has its original rectifier and zener, but there's an un-opened Pod-tronics unit in the box of parts the original owner gave me, so maybe now's the time to install it.

I guess the first step is to replace all the melted ground wires and power it up and see if it works, then go from there. I've given some thought to going ahead and replacing the entire harness ($125 from Commando Specialists), as the wiring was a bit of a rats nest even before the fire. My larger desire is to convert to a negative ground system, which I'll ask about in a subsequent post. Otherwise, any thoughts or suggestions from you guys would be appreciated (except telling me what an idiot I am).

-John

Sorry to see that John, I doubt whether the Boyer is damaged, the engine probably died due to lack of volts! I changed my Interstate over to neg earth a few years ago, done away with the zenner at the same time and fitted a solid-state rectifier/regulator, also a 3 phase stator. The main reason I changed to neg earth was so that I could use a more modern electronic indicator flasher unit, these are not affected by voltage drop which means the flashers still flash when at a standstill in traffic with the headlight on! Good luck with the repairs, probably won't be too bad once you get stuck into it,
Dave.

I doubt too if anything electrical other than the wires were damaged. Just goes to show that no circuit should be left un-fused. Good that the whole bike didn't catch fire. I always worry about the gas catching.

Dave
69S

DogT said:

I doubt too if anything electrical other than the wires were damaged. Just goes to show that no circuit should be left un-fused. Good that the whole bike didn't catch fire. I always worry about the gas catching.

Dave
69S

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Yes, fused on the correct side!

daveparry said:

Sorry to see that John, I doubt whether the Boyer is damaged, the engine probably died due to lack of volts! I changed my Interstate over to neg earth a few years ago, done away with the zenner at the same time and fitted a solid-state rectifier/regulator, also a 3 phase stator. The main reason I changed to neg earth was so that I could use a more modern electronic indicator flasher unit, these are not affected by voltage drop which means the flashers still flash when at a standstill in traffic with the headlight on! Good luck with the repairs, probably won't be too bad once you get stuck into it,
Dave.

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Thanks for the feedback. I'm off to the store to buy some wire and connectors. Hopefully, I'll know something later today.

I've got quick disconnects on both my positive and negative ground bikes, but I use a home-built adapter for the positive ground bikes. That way there is nothing to cap, and the metal pin that is exposed is the ground wire. Sorry to read of your meltdown, but I'm sure you'll get it back up to snuff in no time. 'luck

I had the same thing happen while using the bike battery to power timing light, but caught it before too much of the harness was toasted. No electrical components were damaged and I was able to make everything look sanitary after initial freak out. Lesson, use a battery charger with timing light! :roll:

bmwbob said:

I had the same thing happen while using the bike battery to power timing light, but caught it before too much of the harness was toasted. No electrical components were damaged and I was able to make everything look sanitary after initial freak out. Lesson, use a battery charger with timing light! :roll:

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I just bought a battery powered timing light that runs on two "D" batteries, and love it!

Hang in there Bonwit.
It just happened to me like 3 weeks ago.
A loose and flying washer had lodged beteen the horn terminals and smoked my harness.
I got the deal on C.Specialties "fire sale" on harnesses (i can laff now).
Took a while to figure it out but I got it in place.
All my electrical components were ok.
I tested them first mostly the zener and rectifier.
Fingers were crossed on the Boyer.
I had an over rated fuse in place by the PO.
So it didn't blow either.
I gathered from the forum that a 15 amp is about right.
Not the 30 by the PO. All is good now.
And you emerge with a very knowledeable idea about your wiring in depth.
It was an ironically timed failure as my final body work was going out for paint.
A real setback for me. But have a stiff upper lip old chap.
You'll get thru it with flying color coded wires, chuckle.

You can see my results linked in my sig.
J dog

Thanks for all the good advice. Here's some good news. I managed to replace all the burned ground wires, hooked up the battery and everything came to life. Engine starts and assimilator turns off, so I assume it's charging. A few of the adjacent wires in the bundle had some damaged insulation, but do not appear to be burned through. I'm still thinking about replacing the entire harness as a precaution.

-John

Surfdog said:

Hang in there Bonwit.
It just happened to me like 3 weeks ago.
A loose and flying washer had lodged beteen the horn terminals and smoked my harness.
I got the deal on C.Specialties "fire sale" on harnesses. . .
J dog

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Curious. Was the Commando Specialist's harness exactly like the original? Did it have all the proper connectors, etc.?

John I would change the harness, If for nothing else just piece of mind, And remember to add smoke to the new harness, It will work better. LOL Glad to hear everything is OK. Chuck.

Curious. Was the Commando Specialist's harness exactly like the original? Did it have all the proper connectors, etc.?

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Well I can't tell you that exactly because my harness was already hacked into by one of the PO's.
However it DID match the wiring diagram in the WorkShop Manual I have for the '72 Commando.
The manual covers several models and years but it was spot on along with all the connectors etc etc.
Plus the switch gear and directionals were missing on my bike so those wires were redundant.
I left those wires in the harness for some future owner to bring it back to stock after I'm long gone.
Translating the color codes from the new headlight wiring to the new/different handlebar switchgear was the biggest hurdle for me. But easy enough once I made a chart showing what wires go where to do what. Plus it was cool because I then could lengthen those kludged up wires and cover them with heat shrink so they could extend enough to fit inside the headlight shell for a much cleaner look. Same with the Ignition switch which had been moved previously to the right side forknut mounted on an alloy bracket. I cleaned that all up.

Yeah CS harness was the way to go for me and a lifesaver.
J Doggg.

It happened to me right after surf dog and I got the harness from commando specialties. Cleaned up the look of my bike and went right on . Only took a few hours and a little help from the forum and she's running good as new. Well as good as she was before. Of course it never ends. I just got the caswell kit as my fiberglass tank is leaking. I can't wait to see the results of this. Thanks guys.

If you are thinking of adding the Podtronics and going to negative ground, you might seriously consider building your own harness. Not really that difficult and the original wire color scheme is available in modern wire from British Wiring. You might also consider adding a small 3-4 fuse panel with blade fuses. You can individually fuse lights, ignition, and horn. The glass fuses are getting more difficult to find while the blade fuses are found everywhere. Convenient if you blow a fuse while away from home! (And yes, I'll say it, consider adding relays for lights, horn, and perhaps ignition.)

I have never seen a need to convert to negative ground, but realize that if you are adding certain electronic devices, (LED turn signals, etc.) then it does make life easier.

If your harness is original you have been living on borrowed time for the last 10 years, never mind your current malady. Lucas electrics get a bad reputation for no reason other than parts of them live TOO long, they should have designed a harness that failed in its entirety, along with all the attached components simultaneously, no one else got it right either...

If your machine is stock, and you intend to keep it that way, then get a new harness, a new rectifier, a new zenner and a new capacitor, be prepared to brass brush all the remaining connection points and consider replacing all the swtiches and bulbs; this will give you plenty of time to worry about your ISOs, your engine, your primary, your transmission...What is a Commando if not a work in progress?

I re-wired mine from the get-go, I wanted a totally separate ignition circuit so that a bad horn or high beam wouldn't strand me, I ended up putting all appliances on separate circuits, via a Centech fuse panel, ($39):



I also wired my headlight connected appliances (handlebar switch controled) with 16/18 ga wire routed down the backbone to 20 amp relays so that the high current stayed in the belly of the beast with 14/12 ga as appropriate going to the actual components.

RS