I've noticed over the last week or so, at night my headlights will dim, go back to bright, then dim and repeat. They never fully go off, just dim. I'm clueless of what causes that...any ideas?

 

Are they hid or regular. Ig they are hid you may need a new ballast if they are regular then you may need a new voltage regulator and or alternator.

 

Are you drawing a lot of power when they dim? I.e. speakers, aux lights, etc?

 

They're regular lights. And I do have a 800 watt sub and 2 hella 55 watts but they would act up even when the hellas are off. I sure hope it's not the alternator

 

Disconnect the amp and hella' and check again.

 

My lights used to dim like crazy when the bass would hit in my explorer, apparently if you upgrade the "big 3" wires it helps with this issue

 

https://www.f150forum.com/f75/big-3-...ng-how-174540/

 

I'd have the alternator and battery checked. These alternators were so bad inside that the brushes don't fully contact when the rpms comes down to idle. I would hope that it isn't, but would be betting money thats where your problem is. If the battery is weak, or has a bad connection, it will cause the draw down also. Best to just have them checked. Play it safe.

 

Is it just your headlights that dim or do all lights in the truck dim too? You could take a meter and measure battery voltage with the engine idling or when it is dimming to watch what it does.

 

It's just the headlights. And it's not when the bass hits, or when the hella's are on. They'll just dim at random. And i've had this current wiring and accessories for 2 years and it's just recently started acting up