wiring

Hi, This is my first time on here and need some advice. I have a 69 commando roadster. I took it for a run a few weeks ago with no problems. I had to charge the battery to start it this time. When i was putting the fuse ( negative wire on the battery) back together the the wire was very hot, to hot to touch so i left it disconected. Could some give me some advice on what to look for and what to do.
Thank you, Brett

Hi Brett, welcome! Give us some more info... about you and the bike. What is your skill set? Shade tree? Rocket scientist? Do you know what a DMM is and how to use it? You know the old Brit stuff is POSITIVE earth (ground) , right? We can help you sort it out, more info please :mrgreen:

A wire hot to the touch means it's carrying more current than ever intended, usually a short circuit. Pictures help too! Close up and personal (of the battery and wiring!)

Hi Thank you for the reply.
I have had the bike for a few yrs and this is the first time I have had a problem. I do know a wee bit about british stuff but its been a long time since i have done anything serious with them. When i was younger I restored a few british bikes ( triumphs, and bsa mainly ). I got married and ofcourse everything had to go to finance the house etc. I am an empty nester now so its back into the bikes.
I really dont know how to explain the problem in more detail as i have described it as it is and how i see it.

brett said:

Hi Thank you for the reply.
I have had the bike for a few yrs and this is the first time I have had a problem. I do know a wee bit about british stuff but its been a long time since i have done anything serious with them. When i was younger I restored a few british bikes ( triumphs, and bsa mainly ). I got married and ofcourse everything had to go to finance the house etc. I am an empty nester now so its back into the bikes.
I really dont know how to explain the problem in more detail as i have described it as it is and how i see it.

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1) the battery wasn't accidentally charged backwards? Stupid as it sounds... it has happened. Check with your DMM, red lead on +, black on -, should give voltage reading, reverse them, you should see a - appear on your DMM. Just a long shot rule out here.

2) Quite possible while disconnecting and fishing the battery out, a wire was accidentally disturbed and is now shorted to earth. Did you disconnect any other component? Rectfier? Zener diode?

Troubleshoot by disconnecting things, all the major current supply wires. You have a wiring diagranm?

3) possibly a failed component when last you rode it, took the battery down, and now with a charged battery, is showing itself..


I like to disconnect things to trouble shoot. Remeve wires from the ignition switch, zener, etc. and then measure the current draw from the battery terminal to the lead that belongs on it. Start plugging thins back in will point you to it.

When i charged the battery i removed the fuse and made sure i had the polarity correct ( been cought before) It got hot when i turned the ignition on. I will have a good look at the wires and connections. I can not understand why things go belly up for no apparent reason but i guess thats electrical components eh. When i get some pics i will post them
Cheers

brett said:

When i charged the battery i removed the fuse and made sure i had the polarity correct ( been cought before) It got hot when i turned the ignition on. I will have a good look at the wires and connections. I can not understand why things go belly up for no apparent reason but i guess thats electrical components eh. When i get some pics i will post them
Cheers

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Sometimes this stuff just leaks out, must be topped up from time to time.

LOL yeah everything has a packet of smoke in them. when the smoke escapes its knackered

brett said:

When i charged the battery i removed the fuse and made sure i had the polarity correct ( been cought before) It got hot when i turned the ignition on. I will have a good look at the wires and connections. I can not understand why things go belly up for no apparent reason but i guess thats electrical components eh. When i get some pics i will post them
Cheers

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What is switched on with the key.. lights, ignition, horn open the headlight bucket, look around, remove the fuel tank, look around.. then begin the disconnecting ritual

thank you. first click for ignition is when things get hot. would it be in the boyer ignition? i will go thru the ritual and see what i find. i will do it now and let you know what happens when i get back on line later today. cheers and thank for the advice

If it's still wired as a 69, the ignition switch only switches off the ignition (coils) and the stop lamp. Everything else is still connected through the fuse to the battery. That's why I remove the fuse on mine when I am not riding.

It could be most anything, the hot wire that is. Most likely something has either shorted, or possibly the zener or the MC2 is shorted.

Only way to find out is get a meter and start disconnecting things until the current out of the battery stops. You could also use a 12V bulb as a short finder. Put the bulb in place of the fuse and start pulling wires off things until the bulb goes out. That would be safer.

If it only happens with ignition on, it's got to be the wiring to the coils (Boyer?) or the circuit to the stop lamp. Do the bulb thing so you don't burn things up.

Dave
69S

DogT said:

If it's still wired as a 69, the ignition switch only switches off the ignition (coils) and the stop lamp. Everything else is still connected through the fuse to the battery. That's why I remove the fuse on mine when I am not riding.

It could be most anything, the hot wire that is. Most likely something has either shorted, or possibly the zener or the MC2 is shorted.

Only way to find out is get a meter and start disconnecting things until the current out of the battery stops. You could also use a 12V bulb as a short finder. Put the bulb in place of the fuse and start pulling wires off things until the bulb goes out. That would be safer.

If it only happens with ignition on, it's got to be the wiring to the coils (Boyer?) or the circuit to the stop lamp. Do the bulb thing so you don't burn things up.

Dave
69S

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That said, my gut tells me the wiring to the (all plastic) stoplight switch has shorted. Any other (besides Boyer) modifications done electrically over the years?

"When i was putting the fuse ( negative wire on the battery) back together the the wire was very hot, to hot to touch so i left it disconected. "

Seems odd that if the wire was too hot to touch that the fuse didn't blow. The fuse isn't the cause of the problem of course but as you continue the tracing/troubleshooting you should also check to be sure that the fuse is not higher capacity than it is supposed to be.

mike996 said:

"When i was putting the fuse ( negative wire on the battery) back together the the wire was very hot, to hot to touch so i left it disconected. "

Seems odd that if the wire was too hot to touch that the fuse didn't blow. The fuse isn't the cause of the problem of course but as you continue the tracing/troubleshooting you should also check to be sure that the fuse is not higher capacity than it is supposed to be.

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Yeah, sounds to me like its the wrong fuse. British fuses are rated differently than American fuses. A British 35 Amp fuse will blow instantly, where an American 35 Amp fuse is rated to carry 35 amps continuously. A safe American replacement if you don't have a British fuse would be 20 or 25 Amp.

Could it be that something was left on, draining the battery, and the constant drain while re-charging the battery caused the wire to overheat?

If not, a component may have gone bad, and a likely culprit is the zener diode.

to check the zener, unplug it and check the resistance by placing one lead of an ohmeter on the spade terminal and the other on the stud. With the positive lead on the stud, you should read high resistance, on the order of 5-10,000 ohms. With the positive lead on the spade terminal, you should read infinite resistance. The way the zener works is as the voltage increases, resistance decreases, allowing excess voltage to pass to the z-plate and be converted to heat. If the zener fails, voltage is drawn off the battery until dead or the fuse blows.

I had a zener go bad just last month and blew two fuses before I realized what was wrong

I got the bike going, started first kick and ran well. the fuse holder is still hot. ???????????
cheers

If the fuseholder is making bad contact (which happens sometimes) it will heat up due to the extra resistance created. Try taking the fuseholder apart and clean it along with the fuse ends. (Shine contacts and fuse ends with a metal finishing pad or any scrubby pad and reassemble.)
Russ

I had a Zener Diode go out a while back.
Kept blowing fuses until I disconnected and as soon as a reconnected fuse blew again.
Replaced Zener and Rectifier with a solid state Regulator-Rectifier, 12V,+or-, 1 Phase, Podtronics 200 Watt capacity unit
$49.95 from OldBritts

thanks for the assistance i will look into it further and get the necessary bits.
cheers to you all