Light Fantastic

Greetings all,

I had an interesting experience whilst out on my MK III Commando yesterday afternoon, I was making progress up the A15 towards Sleaford when I noticed that my Hi Beam light was on, this was unexpected as the ignition switch was not set to lighting! This happened a number of times for varying durations.

I had a look at the electrical spaghetti diagram when I got home, but couldn't work out where the fault could be, am not too confident in the voodoo smoke generator/cabling arena (good at letting it out unexpectedly).

Using the Hi/Lo switch & pilot/main switches seemed to make no difference - in that they sometimes had an effect & sometimes not - so the effect of their usage could as well be down to vibration/serendipity, eventually the headlight went off and didn't come back on again. When I got home I checked the switch operation with the ignition set to lighting and all worked normally (perhaps it's haunted & I need my headlamp exorcised).

Has anybody any suggestion as to where I need to look, this bit of a pain as MOT due in 3 weeks, and I'm on the ferry to Rotterdam in 4 weeks!
(Standard UK ignition, Sparx replacement L/H switchgear, Original R/H switchgear)

Mike

MK III Commando

If, as you say, the problem only affected main beam, either power shorted from another circuit to the blue/white [UW] headlamp main beam wire somewhere, or another possibility would be a faulty headlamp flasher switch (combined horn & headlamp flash button) as the headlamp flasher is powered from the main ignition circuit (white[W]) and not the headlamp (blue) circuit.

My Mk3 once turned on its headlamp while I was sitting next to it with a beer congratulating myself on a thorough clean and polish - water in a grubby main switch can be enough to start odd effects. Even with the rubber cover, it never stays dry.

The standard Mk3 loom has far too many block connectors and I pull mine apart each year and give them a blast of switch cleaner, as well as inside the switches themselves.

I suspect that LAB's suggestion is correct on this one but all of the contacts are prone to corrosion. I'd suggest opening the handlebar controls and cleaning as well as you can, plus removing the fuel tank and pulling the connectors apart and a squirt of switch cleaner. It can't hurt and will reduce the chances of problems in the future.

Cheers Gents, damp ignitiom switch is unlikely - bike has not got wet for some time (despite Hobot's aspersions on our weather ;-) I will investigate the flasher

Regards, Mike

'Price of Darkness' has struck again ?
Don't whinge ! When I was a kid we rarely even had working lights on out bikes for long.

acotrel said:

'Price of Darkness' has struck again ?
Don't whinge ! When I was a kid we rarely even had working lights on out bikes for long.

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I can assure you it is "The prince of darkness" I well remember those dark and dim rides on my Ariel 500 twin KH with 6v which would only power side lights :shock:
Oh how I laughed
JohnT