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mysterious overheating of electrics

Submitted by michael_addison on Sat, 30/06/2018
Forums
Electrical

Morning folks,

A worrying thing happened this morning, my bikes are in a garage under the living room of my house.

After a run on my "99" Dommi last week I decided to alter the handlebar levers, remove the petrol tank and adjust the clutch . After these matters were done everything was replaced ( at least 5 days ago) and the bike was left in the garage until this morning when I replenished the primary chain case oil. At this point the case cover was not removed , all I did was open the filler hole and remove and fit the overflow plug at the bottom.

About 1 hour later I noticed smoke coming from the battery box so quickly opened it up to see that the cable covering from the positive terminal had melted and was smoking. With the battery removed I am now at a loss to understand why this has happened.

The wiring on the bike has not been disturbed and the battery has not been touched since being re charged two months ago.

I am still on 6 volts .

Anybody any suggestions please?

Submitted by ian_soady on Sat, 30/06/2018

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There's obviously a leakage to earth somewhere. Given that you removed the tank recently I'd be looking in that area for a frayed wire / stray bullet connector touching earth. It may be that when you topped up the chaincase you moved the bike just enough to let something touch?

If you have a multimeter set it on the ohm range and check between the battery live lead and earth (with battery removed of course). If you see anything more than a few milliohms then progressively disconnect bits of the loom till that leakage disappears.

Submitted by barry_carson on Sat, 30/06/2018

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Hi, when you find out what it was i would fit an inline fuse close to the battery terminal . bit more piece of mind

Submitted by ian_soady on Sat, 30/06/2018

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I always fit the fuse on the earth side rather than the live which means a carelessly wielded screwdriver won't melt the earth wire......

Submitted by michael_addison on Sat, 30/06/2018

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Previously ian_soady wrote:

There's obviously a leakage to earth somewhere. Given that you removed the tank recently I'd be looking in that area for a frayed wire / stray bullet connector touching earth. It may be that when you topped up the chaincase you moved the bike just enough to let something touch?

If you have a multimeter set it on the ohm range and check between the battery live lead and earth (with battery removed of course). If you see anything more than a few milliohms then progressively disconnect bits of the loom till that leakage disappears.

Thanks Ian, also thanks to Barry and Robert.

What puzzled me in the first place was that if I had disturbed anything why would it take several days to manifest itself? The bike has not been moved off its centre stand.

I will do the multimeter test and take the petrol tank off as well as the chaincase and see if I can discover anything.

A fuse will be fitted. I will let you know what I find.

Thanks again,

Cheers Mick

Submitted by michael_addison on Tue, 03/07/2018

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Hello Ian, Barry and Robert.

Stripped the melted wire out of the loom - the earth wire running inside the loom to an earthing point on the frame lug near the battery box holder - and replaced it. No sign of any exposed wire inside that part of the loom.

The rubber around the four way old fashioned connector on the negative line had melted leaving the metal base exposed so I recovered it .Whether the metal base was exposed before the melting I can not say.

Connected everything up and lights, horn and ignition works. Left it standing for about 90 minutes and saw no smoke so assumed it is now O.K.

I have put a 15ampfuse into the positive line between the battery and an earthing point. I can get at the fuse easily so removed it whilst parked in the garage just to be safe.

Any comments would be gratefully received to educate me in the wonders of electrics.

I did put the meter on the negative wiring connector nearest the battery and no significant readings.

Cheers Mick

Submitted by barry_carson on Tue, 03/07/2018

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Hello Michael, if nothing else was turned on when it happened. just wondered if it could be something to do with the horn or brake light wiring connections short circuiting. if they are wired straight from the battery.

Barry

Submitted by howard_thompson on Wed, 04/07/2018

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'I have put a 15ampfuse into the positive line between the battery and an earthing point. I can get at the fuse easily so removed it whilst parked in the garage just to be safe.'

Er, why? If the problem manifests itself again while the bike is parked up the blown fuse will alert you to the fact but with the fuse removed you'll be none the wiser until the (perhaps) intermittent fault re-occurs while you're actually riding it, with less-convenient and possibly dangerous results.

Submitted by michael_addison on Thu, 05/07/2018

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Previously howard_thompson wrote:

'I have put a 15ampfuse into the positive line between the battery and an earthing point. I can get at the fuse easily so removed it whilst parked in the garage just to be safe.'

Er, why? If the problem manifests itself again while the bike is parked up the blown fuse will alert you to the fact but with the fuse removed you'll be none the wiser until the (perhaps) intermittent fault re-occurs while you're actually riding it, with less-convenient and possibly dangerous results.

Good point Howard.

I was just being ultra cautious . I did not want the house going up un flames.

Cheers Mick

Submitted by ian_soady on Sat, 07/07/2018

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You could I suppose put a lower rating - say 5 amp - fuse in while it's parked which will blow long before there's any problem.

Submitted by richard_payne on Sat, 07/07/2018

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I always remove the fuses when parking up. A measure that I came round to after washing the Mk3 Commando one day which had led to water in the ignition switch - I came into the garage an hour later to see the headlamp flashing slowly on and off, with the ignition key in the 'off' position.

I don't really think that it's sensible to be sleeping above any vehicle without the battery being isolated, whether it is new, old, reliable or not. The risk is just too great.

Submitted by alan_osborn on Wed, 18/07/2018

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Previously richard_payne wrote:

I always remove the fuses when parking up. A measure that I came round to after washing the Mk3 Commando one day which had led to water in the ignition switch - I came into the garage an hour later to see the headlamp flashing slowly on and off, with the ignition key in the 'off' position.

I don't really think that it's sensible to be sleeping above any vehicle without the battery being isolated, whether it is new, old, reliable or not. The risk is just too great.

Your first issue is 'washing' it Don't you know that motorcycles and water are very poor bedfellows, Don't do it again.

Al

 


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