Click,Click,Click!

My money is in the compression type terminals. Every toolbox back in the day had this metal tool that looked like a knob. The top came off to expose a 1" wire bottle brush to clean the insides of tour batter cable ends. The bottom would be this scary looking female wire brush looking thing that would go on top of the terminals and screw down onto them cleaning the surface to a bright silver. Clean both sides of the terminal and lug and your clicking will probably go away. If your dome light goes out after it ticks, its surely a battery connection issue.