OEM Headlights Flicker Sometimes (Halogens)

I’ve noticed it before a few times and never really gave it much thought, but I was driving in some thick fog 2 nights ago and it made it more noticeable... Sometimes when I hit the brakes while moving, the headlights will do one very quick flicker. It’s very random, I noticed it twice, maybe 3 times in that half hour drive. I was wondering if anyone else’s truck does this and maybe it caused by the notoriously crappy batteries they put in these from the factory?? Or maybe there’s an issue with my alt?? My truck only has 12K mi. and 1.5 years old, so it’s well under warranty, but it’s one of those problems I know they’ll never reproduce while it’s there at Toyota, especially in the daytime.

 

FWIW I have an AGM + OTT (includes higher charging output for AGM), and my plug-in H9 headlights flicker sometime when tapping the brakes. No idea why.

 

Mine does the same, has since new I believe, never put much thought into it. I'd be curious to see if it's common or not.

 

Most vehicles I've ever owned have done this to some degree. Hitting the brakes turns on lights - more current demanded instantly - regulators aren't 100% efficient and there can be some dampening of supply for short periods of time.

 

keep in mind the Bros and ORs have an electric brake booster. I don't know,,,,, but would guess, this booster draws quite a bit of amps to run.

 

Tell me more. I didn't know this...

 

as far as I know; it's an electric motor that runs a small hydraulic pump, rather than relying on a traditional vacuum powered brake booster. This electric pump is also part of the Crawl Control system,,,, it's the pump and ABS system making all the noise.

 

My '19 OR does it too

 

Interesting; didnt know this could be something I'll have to keep an eye out

 

OP here. Funny this thread finally got some action almost exactly a year after posting it. My headlights still flicker here and there, but it hasn’t gotten worse or anything. My guess is it’s probably just the notoriously weak stock battery these trucks come with. I’m going on almost 2 1/2 years on mine, but I’ve heard of many people having to replace theirs before the 2nd year.