If the freedom of speech is taken away then dumb and silent we may be led, like sheep to the slaughter.

- George Washington

Friday, 11 February 2011

Electrickery 2

Electricity is evil. It is doubly evil when confined within a motor vehicle. The reason for this is that electricity is the cause of proportionately more intermittent faults than any other system. If something rattles, you can find it and tighten it. If something corrodes, you can strip, repair and refinish it. Even fuel faults (which can be little buggers if they feel in the mood) are usually amenable to logic and careful diagnostics. But electrical faults are thoroughly wicked little monsters who disable your ride, and then disappear. Have they gone, or are they still there, waiting for you to reach that dark, fast stretch of rush-hour A-road before stranding you instantly without power or lights?

I mentioned recently that I had experienced a misfire on the XT and had turned back and dug the Triumph out of hibernation to complete the journey. Yesterday, I got out the multi-meter and checked everything. Twice. Nothing wrong. The battery is reading 12.6V, the alternator is delivering 14.4V at fast idle, reducing to 13.2V if I switch on the lights and heated grips. In other words, fine. I took it for a 5-mile ride (up the hill, so if it conked it would be easier to push - I'm not 18 any more), and it behaved normally. I rode it slow, I rode it fast; I lugged it and revved it; I let it run down to nothing in a high gear and then whacked it open, waiting for the gulp and cough that I had the other evening. Nope - it ran sweetly and well.

I took it out to the shops this morning. Same thing. So now I am in a dilemma: do I use it for work tomorrow, as the problem has gone away? Or do I play safe and take the Triumph on the grounds that the gremlins are just hiding and waiting for their next chance to do me some bad?

The only thing I can guess is wrong is the ignition switch. I know the contacts are a bit iffy. Sometimes increasing the electrical load (like switching on the lights) will kill everything, and only switching the key off and on again will cure it. Perhaps that's it.

I have now got a new switch on order from David Lambert, and I will fit that when I next have a day off. In the meantime, I think the Triumph needs a bit of a run. It's dirty again, after all.


  1. "....do I use it for work tomorrow ..... or do I play safe?"

    Sod's Law dictates that if you gamble, it'll be more-risky.

    Wait for the weather forecast. If it's going to be dry, then take a chance.

    I know from experience, there's nowt worse than pushing a dead bike in the rain.

  2. Haven't done that in a long time, although I did have to push the XT in the dry (up a hill) for about a mile with another electrical fault. It's like a game of whack-a-mole: I sort one out and another one takes its place. A rewire is the only long-term solution.

    I'm going to take the Trumpet. It's already wet and dirty, so it won't harm to run it for a few days before I put it away for the rest of the winter.

  3. I used to have fun dismantling switches, and (sometimes) getting them back together again. Obviously depended on how many little springs and ball bearings went flying....

    Contacts can do funny things - if they pass very little current a "skin" of oxide can form, which obviously can cause faults. Too much current will overheat them, and burn the faces when they part.

    I had an interesting example of this with my old Austin Maxi (don't laugh, it was a very roomy & versatile barge, and incredibly capable in snow). Like most of it's ilk the points would need regular cleaning and resetting, so I bought a simple electronic ignition kit from Maplin which just used the points to trigger a transistor switch. Despite having contact "wetting" resistors (which pass a small current through the points) I found that after a few months it would missfire or refuse to start. It needed either a quick application of some fine emery paper, or reconnection of the coil directly to clean the oxide away...

    Another thing with contacts is whether they move across each other, or simply pull away. The former increases wear, but keeps them clean, the latter can give problems as I described above with low current applications.

  4. I haven't dismantled the switch, but from photos I have seen the contacts are bumps in a piece of brass which are brought into contact by sliding together. The key mechanism is worn and sloppy, and it looks (guessing here) that the contacts are dirty and can fail to contact fully in a random way, leading to the occasional high-resistance joint which fails under higher current.

    But I speak with the authority of someone with a Grade 8 in Physics O-level, so I appreciate your comments.

  5. Can't remember what grade I got in Physics, but it was my second favourite subject after metalwork. I was fortunate that my grandfather was a founder member of the local model engineering society at the turn of the last century - I spent much of my childhood round his house and workshop.

    I like to think I aquired his ability to design things in my head, rather than having to spend hours at a drawing board first.

    Anything marked with the words "No user serviceable parts inside" is fair game, as far as I'm concerned!

    If the ignition switch has any small holes leading to the innards, a squirt of Servisol contact cleaner often works wonders. Failing that try some WD40...

    If you aren't too bothered about the security side of things there's no reason why it couldn't be replaced with any other sort of switch, or switches. Remember the ghastly device on the Jawa? - the one that only needed a coin and a six inch nail to operate!!

  6. Heh. I just didn't 'get' Physics at all in those days. Now, it fascinates me (same with History, mind). Lousy teacher, immature brain, not even a bare pass. If there are any holes, they are inaccessible. I have flooded the thing with contact cleaner and WD40, and I have lubed the key with silicon spray, but it has made no difference.

    I considered a simple toggle switch, but the Yam isn't a field bike - yet. I've got a new switch on order. Plus dismantling the yokes will perhaps let me find the persistent high-frequency buzz that has been driving me bonkers for the last year. (Perhaps it's the old switch!)

  7. If it's any comfort, I have O and A level Physics and neither have ever been much help with bike electrics - or, as we like to call it, voodoo.

    Which is why it wouldn't surprise me hugely if it was the ignition switch, even though it probably shouldn't be. High resistance at constant voltage on a universal circuit drops the current across the board, so it should manifest either across all the electrics or, most likely, when trying to crank the starter. But it just might be the "run" rather than "start" contact (or wiring) which is just grubby enough (or worn enough) to drop current below the necessary coil draw without visibly affecting lights, dash or indicators.

    Empirically though, my experience of misfires is coil - HT lead - plug. Usually coil. Any other ignition problems are reg/rec. I'm sort of hoping my troubleshooting flowchart never needs to go much further than that...

  8. Here's a clue for you, something I noticed a few days ago. If you touch the brake lever/pedal with the headlight on, the headlight gets slightly brighter. That's telling me there is a poor earth somewhere, and the headlight is finding an earth through the brake light circuit. But of course that could be complete balls. The switch is known to be dodgy anyway, so replacing it is worth doing, and I will have a check/clean/grease of all the contacts and earths while I am in there.

    Litle by litte, the bike is being improved, much against its will.

  9. Litle by litte? That's Chaucer, that is.

    Or 7.04 am.

  10. Ah, the benefits of a classical education! Being able to think of Chaucer at that time of the morning has to be some kind of endorsement...!

    Could indeed be finding a better earth through the brake light circuit, especially if it does it at higher revs. At idle or low revs it might just be the extra load from the brake light causing the reg/rec to step up delivery to the next notch.

    I don't disagree with the idea of replacing the switch as first port of call, though - always best to eliminate known problem areas first.

    Struck by a pang of conscience this weekend I spent a few hours Saturday cleaning the bikes and I can thoroughly recommend SDoc100. Hadn't used it before, but it's like a super version of Wonder Wheels for shifting all sorts of grime. Not only that, but neither bike seems to have dissolved so it probably is as bodywork-friendly as it claims to be.

  11. It's at idle, specifically when I stop to open the gate and the light shines on something close. It's not noticeable in normal riding. I didn't realise the reg/rec worked in steps (thought they were analogue in operation), but that might explain it.

    Thanks for the info on SDoc100. I haven't tried that either, always used Muc-Off or Castrol Greentec, which have been fine, but always good to hear of something better.


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