Help diagnosing charging system issue

Hello, I have a 2006 Tacoma (2.7 L, 2WD, base model) with 387K miles. I am having some charging system issues that started with an intermittent battery light on the dash.

The battery is about three years old, rebuilt alternator from a trusted source put in about four years ago, and drive belt is about a year old.

I took it to the local shop to do a test of the charging system, and the battery, starter and alternator all tested good and under full load as well.

I lost power while driving yesterday and had to be towed back. No codes thrown to date.

I don't have a good place at the moment to work on the vehicle while staying in an apartment building nor transportation to get to a parts store, but I am hoping to do some basic diagnostic steps before finding a hopefully more reliable shop.

May I get any input (or links to resources) on where you would start with diagnosing the issue? Thank you for any advice.

 

I would double check that all the cable/wires are tight and clean, especially the battery.

 

along with a thourough voltage drop test on every battery cable

 

I wonder if a bad or worn out ignition switch could cause your power loss issues? Maybe something to look into.

 

Thanks for the input so far. Truck started right up this morning when going to work on it. So the battery was charged and it must be something indicating that the system is losing power. I have cleaned the ignition cylinder best I could (and will have the switch tested), cleaned the battery terminals/connectors (and will have voltage tested at each battery cable), cleaned the alternator wire harness/connectors and checked fuse box for any noticeable issues. Everything has looked good. Last thing is to test the alternator pulley for the sake of it (although no noises and belt turning straight with no noticeable issues with all pulleys engaged.) Thank you again.