Charging system issue..?

[Tyler46]

I'm having an issue with my truck. When I'm sitting at idle all my lighting seems to dim and get brighter. So my cluster, radio, and headlights get dim every few seconds and then the truck picks the slack back up, at about 1 second intervals. My idle doesn't drop at all. It stays at about 800 and doesn't drop with the dimming of the lights. When I Rev my engine it smooths out to 800 instead of dropping and coming back up.

Also it's a 2007 Regular cab 2.3 Duratec and 5R55E
And if it helps I don't have the bells and whistles (power doors, mirrors, windows, etc.) Hope this was detailed enough.

[riscorpian]

Grab a multimeter, and measure the battery voltage after letting it sit overnight. Also run the headlights for about two minutes to kill any residual charge before taking a measurement. You should see 12.6V, or very close to that. Then, start the engine. It should dip to around 11V and immediately jump to around 14V, and gradually start dropping down a bit. There shouldn't be any spikes at all. Watch it for a few minutes and see if it starts jumping around. That would signal a bad battery or bad alternator.

Alternatively, you can just throw it at an auto parts store and ask them to check anything. They'll usually check the battery, charging circuit (alternator included), and starter for free right there in the parking lot.