The edit wasn't for you
If the courtesy light is coming on at random, that is a bigger issue than you might think.
Every time that happens, it reactivates the "consumer switched off" circuit, and it's probably happening when the car is off. That would drain the battery fairly quickly.
You need to fix that door latch. In the meantime, watch this video (and don't worry so much about battery voltage...voltage drop/current drain is what's important):
https://m.youtube.com/watch?v=lRcj1fQcWwU
