Interior Light Wiring Issue

[titanfs]

I am worried about another short in the car after my auto shorted out, especially now when I have completed the manual ABF transplant. I have visually check all the internal ori wirings ( doors and terminals K/L/M) while the dash forward are all from the halfcut.
I have disconnected the negative battery terminal and placed a test pen in between the wire connector and the terminal. Opened my vento trunk lid, it glowed very bright, when I closed the lid, the test light went dimmer but it is still glowing and it wont go off unless I reconnect and disconnect the negative terminal.
As for the other door switches and things like head lights/signals, the test light will glow and then completely go off when I switch them off.
I have tried with a separate supply to the trunk light, from fuse box terminal Y, same thing. And as far as i can tell, none of the relays was clicking when I am doing this. I do not have the central locking module nor alarm. I have rechecked the latch switch and the wire running into the trunk lid, they are all ok.
What could be the cause of this?

[Golf Loon]

Sounds like rsidual current. Like a capactor it slowly leeches out power. Then when you put a draw on the current, it is all used up and is discharged.

[titanfs]

Thank you for the reply

Well, guess what ... my coil pack shorted the negative wire melted some wires in the loom. After a 30km trip, parked for lunch, then when I cranked, symptoms like a flat battery (I know it's not coz mine's new), then saw some white smoke across the windscreen ... I'm speechless, such luck. Rewired the few wires, currently using the coil pack from the old 2E.

Has anyone tried the test pen method to see if the light thing is normal? Thank you in advance if don't mind resetting your radio and clock

[titanfs]

The issue I am currently facing is the 12.5V required for the immo to work and the car to start.
I have changed new battery about 2 months back, everything's fine, showing 12.88V on my multimeter, now it's reading 12.58V and the car refuses to start, there's enough current to crank and crank. I swapped to a 120 amp alternator also didn't help as the voltage will drop to around 12.5V after 2-3 days if I'm outstation and don't drive the car.
I don't want to jump start the car everytime nor do I want to try my friend's crazy suggestion of having 9 1.5v batteries to supply 13.5v to the immo.
Please advice. thank you.