Here, give some time, I'll give you a diagram for a circuit that will do the following:
- Work with 12 Volts. Can tie grounds to frame.
- Keep the status LED on when the tail gate is closed (to verify the system is working).
- Blink the LED when the tail gate is open.
- Trigger mechanism is magnetically based (Hall effect sensor), having no moving parts. It will depend on adding a magnet to the tail gate.
https://imgbly.com/ib/N2t5thqMdp
BOM: Allergo A1121 555 timer (18V+ tolerant) LED 2 * 2.2k resistors 1 * 3.6k resistor 1 * 1k resistors 1 * 220k resistor 1 * 2.2u capacitor 1 * 0.01u capacitor
You sir, are the fucking man. That's what I'm talking about!