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Brake light problem, Help please

Ed White

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Changed the scruffy rear wings on my old ex racer. Unplugged lights,  plugged back in,  all good but no brake lights. It passed mot last weds so I'm assuming they worked then. I've put a multimeter on one side of the pedal switch and it only shows a fraction of one volt? With the pedal down and the switch open it reads the same voltage at the other side. So it's like the switch isn't getting a 12 voltage feed, but is getting a very small feed. Help please,  I'm lost now? Cheers Ed 

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Faulty switch is a very common problem. Remove both wires from switch and with ignition on touch them together. If lights work switch is broken. Replace with a better quality one from Car Builder Solutions. 

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1 Incandescant lamps or LEDs?

2 Do you have the wiring diagram and fuse layout, and if not would you like a copy?

3 Did you remove the fuse before doing the work? Check that it's there, seated and not blown

4 As above: Ignition ON then connect the two wires at the switch... do the lights come on?

5 Ignition ON: what's the voltage between the input side of the switch and a good earth? With the same setting what's the reading across the battery?

6 Ignition OFF: set the meter to some resistance range and measure the resistance across the switch with the plunger relaxed and then pressed.

7 While you're there watch the action of the pedal on the switch: does it look adequate? And does the switch feel smooth when you close it by hand?


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Turned out to be a fuse, thanks folks, but didn't come across as a fuse as during my first test with the multimeter it recorded a small amount of voltage? Never mind, all sorted. I learned a bit from reading previous posts. I now know how to check resistance. Every day is a school day

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The low voltage on the brake light switch could be a sign of a bad earth, and the circuit is earthing back through the brake lights (and the other bulbs).  It may be worth removing the fuse again popping the meter on the switch and seeing if you can remove that small voltage with a cleanup of the rear light earth connections. 

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