M818 chasing electrical problems

[Brutacus]

Driving the M818 around today, nothing long distance about 20 miles or so. I've noticed several electrical problems while driving around. The first was ALL the lights went out. All the lights, headlights, park lights, turn signals, brake lights, and dash lights! They came back on, and I returned home and made some observations. While parked, the lights shut off by themselves twice. Both times I had to turn the light switch to the off position and back to the on position. I swore I heard a click sound when it turned off the second time when the truck was parked. Any ideas as where to start would be appreciated.
My other problem is a little easier to diagnose. My passenger side rear turn signal does not work. My brake lights work, but the turn signal doesn't. I was thinking of examining the plug for the rear harness, checking for a cut/frayed wire in the back, or checking the plug for the turn signal switch.
I recently did an upgrade on the alternator with a delco 100amp 24v replacement. I had problems with the rear turn signal before the upgrade, but nothing with ALL the lights going off.

 

[NDT]

The brake light and turn light are the same filament, so this means the lamp unit and the chassis harness are OK. This problem is often caused by the turn switch handle.
The other issue is a short circuit SOMEWHERE in the lighting circuit on the truck. It could be anywhere. See if it only happens with the lights on, that would eliminate a lot of searching. The click you heard is the self-resetting circuit breaker inside the 3 lever switch.

 

[Brutacus]

The lights cutting off only happen when the lights are on. Is it possible for the 3-lever switch to be going bad, or could I have short somewhere that gradually overloads the lights? For the turn signal, I'll start checking at the turn signal lever for the short. I do have a replacement plug for the turn signal, but I don't have the tools for removing and replacing the pins. One thought I have had was switching some of the light bulbs over to LED bulbs. I know those don't pull the heavier load as incandescent bulbs do. Just a thought.

 

[Brutacus]

I just found my copy of the wiring diagrams for the M809 trucks. I'm going to start checking things from the back taillights, trailer plug, wire harness for cut wires, going all the way to the turn signal lever. I Do have a LED test light pick, but that's it. Would I need a multimeter for this test? If so, any recommendations would be appreciated.