Headlight inoperative -- dimmer switch failure and repair

[lragan]

For no obvious reason, when we turned the ignition "on" to start our wildflower ride, the headlight would not come on.  Did all the usual check with fuses, etc., and traced the problem to the dimmer switch.  Voltage went to it, but none emerged, in either position.

Here is how to fix it, without buying a whole 'nuther unit to replace horn switch, turn signal switch, and dimmer switch all in one expensive unit.  

Take the two Phillips screws out, split the housing and observe three small screws that hold in the dimmer switch and a strain relief for the cable going to it.  These are not Phillips, although they look like it.  They have shallower slots.  A Reed & Prince pointed screwdriver fits them well.  Remove them, and the switch will come out in your hand, wires still attached.  Notice how it fits into the housing before you remove it.  

Then observe that there are two tabs in slots that hold the switch together.  Carefully spring these loose, and the switch comes apart in two pieces.  The switch is essentially triangular, with one solid piece of hard brass with raised bumps that engage flat contacts on the other piece.  While the two output connections are wiped with each throw of the switch, the input "wiper" connection merely rotates against the flat contact.  This was corroded on my bike, with a black coating on it.  

Take a small piece of very fine sandpaper --  (NOT emory -- which is conductive) -- I used 1200 grit-- and polish all the contacts -- both bumps and flats.  Then rinse with contact cleaner -- I use the spray can type -- to get all the grit out of the works.  Then snap the switch pieces back together, engaging the two tabs to hold it together.

When you replace the switch in the housing, you will need to gently pry on the plastic extension tab of the switch, which is designed to ride against a fin in the housing.  This provides the contact pressure to assure firm contacts between the bumps and the opposing flats.  Reassemble the whole works, and voila! -- should be good for another 14 years or so.

[Charles S Otwell]

I'm having similiar problems with wife's Magna, but with hers the light comes on when you turn the key on goes off when you hit the starter button like it's supposed to but doesn't always come back on after it starts. So far killing it and restarting it usually takes care of the problem. I imagine it is just a matter of time until that no longer works, I'm hoping mine is as simple as a dirty switch, but I'm thinking starter switch instead of dimmer switch, but I'll definently check out both.. Glad yours was an easy or should I say inexpensive fix ..

[lragan]

Charles, from your symptoms, I would guess it is the normally closed contacts on the starter switch, that open up when you start the bike to turn the lights off.

I have no experience with this switch, but you might try anointing it in contact cleaner.  Good luck, and let us know how it turns out.

You really don't want this to fail after dark...

[Charles S Otwell]

No I don't either, but I think her 55 watt lights would get her home. I intend to take it apart before our next ride and check it out, as not  to err from the safe .

[lragan]

Ah, yes -- the other lights would do that -- if I hadn't wired them to a relay off the high beam lead to avoid putting in a separate switch!  Maybe not so clever an idea, huh? 

[Charles S Otwell]

I wired off the ign switch, used the in-line fuse and the switch that came with the kit, that way she don't forget to turn off the lights when she kills it but still has the option of not running them when chooses. Over a year with no problems..