Dash lights, all cabin lights, headlights, all flicker when im at idle and warmed up.

My first thought was alternator, but I read on another forum that a test you can do is turn the Key to AC, note where battery dial is at, when you fire the truck up the Battery dial should jump up significantly from where it was on AC, if it does this states the charging system is working. I tried this and sure enough mine jumped up from about 10 at AC to 15 running.

Would anything else cause this?

 

Is it a really faint flicker or is it very noticeable?
Mine does this too, and I've noticed it increases whenever my battery is either crusted up or the ground is loose. (I need new clamps this summer. )

 

Its faint, if you dont look right at the dash you dont really notice it.

My clamps are clean, but very old and getting brittle, you can turn them on the battery posts even when they are tight.

My battery itsself is less than a year old, and was recently tested.

 

Mine is the same way.
I am beginning to wonder if those are our problem. lol

 

Try removing the clamps from the battery. Put some aluminum foil over the posts on battery (NOT CONNECTED TOGETHER), reinstall clamps. See if that tightens them. If so, check to see if the flicker is still there.

The foil will fill the gap between the post and clamp.

 

And check grounds to frame, fender, and firewall....

 

I get that but ONLY on my map lights. Everything else is steady. I re-did all my grounds with new wires and all, significantly improved headlight brightness and the starter's cranking power, but the faint flicker remains. It seems unchanged by engine RPM too.