Nominal voltage for brake light?

[Redneck]

Okay i blew a bulb on my brake light. To make sure it was just the bulb I checked voltages at the socket. On the running light I had 0 when of and approximately 12V when on. Good to go. Then I checked the brake light and it read 4 volts with brakes not engaged and then 12volts when I engaged the brakes. Is there suppose to be a nominal voltage on the brake light? Inquiring minds want to know.

Paul

 

[Agemax]

it should be 0v with the brakes off and 12v with the brake on, sounds like 1 of your brake light switches has a bad connection or a short somewhere

 

[Redneck]

Kind of what I figured but wanted to ask to make sure before I go digging into something else that may way lay my inspection. Have to get inspection stickers before I can take the rider course on base.

 

[Agemax]

what bike is it. do you have a front and rear brake light switch? if so disconnect one at a time and then check the voltage at the bulb socket. this will tell you which switch is at fault

 

[tkent02]

It could be the voltage from the tail light not being grounded correctly. Disconnect the tail light power wire, check the brake light voltage, I bet it goes to zero when the brake light is off. They share a common ground path, so resistance in the path from the light to the frame will let the tail light voltage raise the voltage on the brake light bulb a little bit.

If that is the case, cleaning all the grounds involved should do it.