On modern car, usually a buzzer warns you when you leave your lights on while leaving your car. Unfortunately on our oldies, such devices were not always available. That could result in a discharged battery... After having left a couple of time the lights on (but been lucky enough to not have a completely flat battery when returning some hours later), I have decided to install a warning buzzer. Theory: I am using the wiring diagrams from Advance Auto-Wire (document here ). My MGB GT is a 75 UK model. The correct wiring diagram is the one on sheet 31 (page 32 of the pdf file). We want to add a buzzer that detects the parking lights are on when the door is opened. That means we need to connect a buzzer between the parking light feeding wire and the door switch. The parking lights feeding wire is a red & green (RG) starting at the "HEADLIGHT SWITCH", the door switch wires are the purple & white (PW) "COURTESY LAMP & DOOR SWITCHES".
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