[Toomanycars]

Problem... No brake lights working on Sierra...

I have 12+ volts at rear connection pin when brake pedal is pushed down and an earth wire direct from battery...BUT... when I connect test light or bulb they won't light up... I also have 12+ volts coming from next pin which is for tail lights and using same earth...test light lights up and so does bulb.....What the @#$%^&* is going on.. It's hurting my brain...

[tanshi]

brake lights are negatively switched arent they?

[losfer]

No they are positive switched theres only one earth for the brake/tail lamp

[fordem]

Toomanycars wrote:

Problem... No brake lights working on Sierra...

I have 12+ volts at rear connection pin when brake pedal is pushed down and an earth wire direct from battery...BUT... when I connect test light or bulb they won't light up... I also have 12+ volts coming from next pin which is for tail lights and using same earth...test light lights up and so does bulb.....What the @#$%^&* is going on.. It's hurting my brain...

You MAY have a high resistance connection somewhere along the wiring - most test meters will have a very high impedance and will draw very little current, a test light on the other hand is low impedance and a high resistance connection will not pass enough current for the lamp to light.

Get under the dash and find the brake light switch - using the test light probe both wires, one should light the lamp all the time, the other only when the brake is depressed, if you don't get light on either one you need to work back to the fuse panel, if you get light on both, you need to work towards the back of the car, if you only get light on one, the switch is the problem.