Rear turn signal stops flashing when brake pedal is pressed

Watch the lights while a helper presses the brake pedal and you'll see unusual things happening. Suspect a bad ground. After the current goes through one bulb, if it can't get to ground, it will find a way there through another bulb. When that second bulb is turned on, voltage appears where the first one had found a ground. When voltage appears on both sides of the first bulb, it turns off.

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