Unpredictable headlight

[Fiat Lux]

The headlight on my 2001 Valkyrie Standard with nearly 55,000 kms has started acting up. Sometimes it works perfectly and sometimes no high or low beam. I use a Kissan modulator and I seem to notice the problem when it is dark. I also have a Cobra light bar and the two seal-beams flanking the headlight work perfectly even when the centre light is out. I took the starter switch housing apart and it seems to be OK. What should I test next?
Fiat Lux

[Bighead]

I would still lay money it is the starter switch

[saddlesore]

With a modulator you have a sensor to turn the modulator off at night.  Could there be a light source that's affecting the operation of the modulator?

[gordonv]

Remove all the extras from the system and see if it still happens.

The extra lights should be run through a relay.

[R J]

1st thing I'd unhook is the modulator.

[Mr.BubblesVRCCDS0008]

I had a bad ground on my headlights and they would act up now and then. I ran a seperate ground  from headlight to the frame and problem went away.

[Patrick]

I too would check for bad grounds and unhook the modulator.

[Fiat Lux]

Thanks for all that advice. The headlight is now working fine. Laugh or cry?
Fiat lux

[Bighead]

Well what was the problem/solution? Inquiring mimes wanna know

[Fiat Lux]

Sorry, I never did give you folks any satisfaction. I took the starter switch apart a second time with greater confidence. I cleaned it again, more carefully and pried up ever so slightly on the tiny copper contacts, improving the pressure applied when the switch is toggled. Put it all back together and all is well. Another month and I'll have the phat lady back on the road and dodging all of last winter's sand and gravel.
Fiat Lux and thanks for the advice

[Chrisj CMA]

Sorry, I never did give you folks any satisfaction. I took the starter switch apart a second time with greater confidence. I cleaned it again, more carefully and pried up ever so slightly on the tiny copper contacts, improving the pressure applied when the switch is toggled. Put it all back together and all is well. Another month and I'll have the phat lady back on the road and dodging all of last winter's sand and gravel.
Fiat Lux and thanks for the advice

The problem will happen again!

[Chrisj CMA]

Sorry, I never did give you folks any satisfaction. I took the starter switch apart a second time with greater confidence. I cleaned it again, more carefully and pried up ever so slightly on the tiny copper contacts, improving the pressure applied when the switch is toggled. Put it all back together and all is well. Another month and I'll have the phat lady back on the road and dodging all of last winter's sand and gravel.
Fiat Lux and thanks for the advice

The problem will happen again!

I will say again.  I just did one yesterday.  A starter switch does not have to be dirty, corroded or anything to be NOT working.  Even a brand new one can have this problem.  

The fact that you said you pried the contact up means its stuck.  Soon it will get mashed down again and you will be back with the same intermittent problem.  You need to do what I had to do on my friends bike.

I took the switch apart, it was about as clean as you can get one....like new even, the problem was the little bouncy contact thing wasn't very bouncy.  It was stuck in its slots and mashed all the way down.  The little tiny spring couldn't push it up to make contact with the brass contacts.

I cleaned out the slots with a sharp knife and made that thing bouncy again.  Worked great after that.

[John Schmidt]

Here's what you need to do to help prevent future failure due to high amperage passing through the start switch from the headlight circuit. In the link, scroll down to the box with Start Switch Safeguard and use the directions to install a relay in the headlight bucket. It removes the major amount of amps from the start switch and instead passes it through a relay built to take 30-40 amps. Then the only current borne by the start switch is what's needed to activate the relay, a fraction of 1 amp.

http://www.rattlebars.com/mtz/starter.html

[MarkT]

Here's what you need to do to help prevent future failure due to high amperage passing through the start switch from the headlight circuit. In the link, scroll down to the box with Start Switch Safeguard and use the directions to install a relay in the headlight bucket. It removes the major amount of amps from the start switch and instead passes it through a relay built to take 30-40 amps. Then the only current borne by the start switch is what's needed to activate the relay, a fraction of 1 amp.

http://www.rattlebars.com/mtz/starter.html

Chet's method protects the starter sw but not the hi-lo switch. You can reduce the amp load on both switches by putting in a relay between the headlight load and it's blue (hi beam) and white (lo beam) supply lines. You can protect both switches with one relay, if it's a 5-pin with 87 & 87a contacts.  (Though that method won't shut off the headlight draw while starting, which you really need if the battery is weak). Otherwise you need a relay for hi & another for lo - really the better method and what I used for mine.  If you need wiring specifics for the former, speak up and I'll explain in more detail.  http://www.horseapple.com/Valkyrie/Tech_Tips/Headlight_Upgrade/headlight_upgrade.html  I installed relays on mine in '98 and have never had a switch problem even while also upgrading the headlight bulb to 130/90watts at that time.