What is so special about this circuit? Well, the first third-brake light I installed I had to pull a wire from the Third Brake Light all the way underneath the carpet to the brake-pedal-switch and I thought it would be easier to pluck the signal of both brakelights via the trunk.
Bench-test your circuit first and apply power to the circuit, with the brakelight connected, for at least a couple of minutes. If the two SCR’s are getting hot (depending on the type of bulb(s) in your 3rd brake light), mount coolribs on them. I used the NTE5483 which is a 8A, 200Vrm type.
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