Headlights/ Parking lights warning buzzer

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".

As the car headlights cannot be switched on without the parking lights been switched on previously due to the switch, we do not need any additional wire:

Basically, the bill of material is as follow:
- buzzer (x1) (electronic buzzer dc 6-15v for example, with 2 wires, for a price of 2.5£ maximum),
- diode (x2) (general purpose diode type 1N4001 will do the job. see here for details about diodes, around 2£ for 25U/N)

- solder sleeves (x2) (for connection of diodes to the buzzer)
And we will use the existing connections of the headlight switch and door switch.

See you soon for the installation on the car!