Tracking down a power drain

[MikeD03Ram1500]

My 2mo old battery is dead. Previous owner installed a security alarm and I noticed a random switch under the hood, but I don't have clue as to what it's for. I've been watching videos about parasitic drains and will be trying it tomorrow using a voltage/multimeter. Any insight you might care to share about how to go about tracing the wiring done for the security system and power drains in general is greatly appreciated.

Thanks - M.
Mike

 

[Bloody_Knuckles]

What you need is a clamp-on ammeter that reads DC current. You can isolate the wires one at a time.