Q&A

 Master

When lights are turned on and brake or turn signal operation alters the brightness or causes other lights to operate the problem is nearly always a bad ground ,(or ground at the bulb holder), or an incorrect bulb fitted (for instance a single filament bulb fitted in the socket where a double filament bulb should be). Try removing the rear lights bulb holders look for corrosion due to perhaps water leaking in through a lamp or seal, also try pushing on and off the electrical connections at the lights a few times to see if it improves conductivity.