Brakelamp switch voltage specific?

[KJDonovan]

Guys,

I need an electrical sanity check... I never have problems with electrical stuff on bikes, it's the one thing I can sit down and draw a picture, go out to the shop wire it and it works.  Not today!  A couple of weeks back I bit the bullet and shelled out for an MZB for my 72 Jack Piner, I was just tired of getting caught out after dark and not being able to see unless I was WOT.  Anyway, got it all installed (getting the timing set right without the woodruff key was an adventure, but that's another story) and needed to do some wiring modifications, as the MZB has a single lead for all the electrical components from the regulator and my old motoplat had 4.  So I run the single power lead into my handle bar switch, the switch has a single wire coming out for the taillamp, so I split it into 2 to accommodate, both the brake and tail lamp.  Start up the bike, awesome spark first kick, headlamp hi and lo beam work great, tail lamp is superbright I am basically a happy camper, until I step on the brake pedal, and instead of the brake lamp lighting, the tail lamp goes out and the brake lamp does not light.  So I pull out the multi meter, check the grounds, good.  Check the taillamp switch, good.  I even bypassed the taillamp switch to make sure both sides of the taillamp bulb worked, again all good.  So I sat there for a few minutes thinking about everything, all the bulbs are 12V why the hell is this happening?  So I basically and down to the brake lamp switch, it tests good and always worked fine with the old motoplat, so now I am questioning if this switch only works with a 6V source.  It's the little square one that Al sold for years.  Is there something more inside these things that a normally closed switch that would cause this type of behavior?

Thanks,

Kevin

Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner (My Ride)
72 Six Day (Wifes Ride)
71 Suzuki TS125 (Project)

[t20sl]

Kevin:
Switch does not care if it is 6 or 12 volt.  Problem could be not enough amperage to run the large wattage brake filament.  Disconnect wires going to headlight and try again.  If brake works better then the output of stator can't handle that much drain.  You could try and find a lower wattage brake/tailight bulb or change out to LED bulb if you find one that runs on AC???.  
Ted

[KJDonovan]

Ted,

The tail / brake lamp is an LED very low draw.  Also when bypass the brakelight switch the brake and tail both light fine, thats why I was thinking the switch.  Maybe the brake lamp switch has some kind of short in it.  I will order a new switch and give that a try.

Thanks,

Kevin

Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner (My Ride)
72 Six Day (Wifes Ride)
71 Suzuki TS125 (Project)

[Richard]

You might check your wiring at the taillamp, you could have the power to either the brake light or tail light connected to the tail light assembly's ground. When you close the brake light switch, you would have power on both sides of the tail light, and no electorn flow, no light. Use an ohm meter and find the brake light assembly's wire that connectes to the lamp scokets base (with the bulbs removed) and make sure it's going to ground.

[KJDonovan]

Ok, mystery solved, I found another old brake lamp switch, swapped it out and it works fine.  I am guessing it just had a short inside it.  Kinda screwy as it tested fine, still does.

Thanks,

Kevin


Kevin J. Donovan
Foster, Rhode Island
72 Jack Piner (My Ride)
72 Six Day (Wifes Ride)
71 Suzuki TS125 (Project)