Jackfit

Hi, I need some opinions on where my brake light circuit is getting current from when the brake pedal is not pressed.

I have audio vox crusie control and it requires a current signal from the brake switch lines to work.

One wire (red) goes to the hot lead into the brake switch, Has constant 12 v DC to it.

The other (purple) goes to the other side of switch. 12v DC when pedal is pressed, circuit complete. 0 v DC when pedal is released.

When I put on my parking lights or headlights, the 0 DV side of the switch now shows 5 v DC .....without the pedal pressed.

The brake bulb does not light, but it is enough current to cause the Cruise Control unit to turn off as if you had stepped on the brake.

Where do you think I am getting current from when I put on lights?

All my bulbs work and light front and back. They are not LED's so there is no lack of signal when brake is pressed. Just current jumping into the white wire leading to brake switch when lights are put on.

Jack

65GGvert

The only path between the lights and the brake lights is the ground. It sounds like your cruise control is allowing 5 volts on the switched side of the brake switch when lights are on. Are you sure you don't have any physical connection to any tail light or other bulbs that light with the headlights and the cruise control power? Where is the cruise grounded? Double check that the CORRECT bulbs light with the lights and the brake lights in case you have a bulb, particularly in the rear that is feeding across a filament or a ground to the brake lights. However if the voltage shows up with the brakes off, you should eliminate the car wiring by disconnecting the power from the cruise from the switched side of the brake switch and see if you get voltage on the white wire in the car when you turn on the lights. If you do, there's a problem with the car lights, if you don't, there's a problem with the cruise system. While you've got that wire from the cruise off, measure on the disconnected wire to see if you get 5v on it when you turn on the headlights. If so, you know it's coming from inside the cruise control. With that wire off, you can eliminate one or the other as a path.

Jackfit

Will check wires again as you suggest.

Jack

BD104X

Just because your bulbs light up doesn't mean they are good. You could have the two filaments shorted and back feeding the circuit and the bulb will still glow. Try it with the bulbs out or just change them to rule it out.

Jackfit

Hi, I have taken one rear bulb out with no change, I am having a problem with the other rear bulb, stuck in socket, will test other wires today before I break the bulb to get it out . Both filaments light , brake filament does not seem to glow when parking lights are on. But the socket is old and may have corosion.

Jack

Frankie the Fink

Put some dielectric grease on those bulbs when you reinstall them Jack. It keeps them from tack-welding themselves into the socket...