Headlights slightly dim when pumping brakes....brake booster?

After I got some work done to the Taco where they installed an LED light bar, backup lights, and a couple switches I noticed that when pumping the brake my headlight dim very slightly. It almost not noticeable, but if you look for it you can see it.

The shop says they did not splice into any factory wiring for these LEDs and switches which from my own research seems to be correct.

I am not sure if it had always done this or if I noticed it after the work because I was more aware and looking for things that were wrong? It does not do it on the first brake pump, sometimes on the 2nd pump, but almost always on the 3rd brake pump. I am doing these pumps in fairly rapid succession. I first noticed when I was going down a steep hill and did some light brake pumping as I went down. It doesnt have to be heavy pumps. Even if I just feather it in a somewhat rapid succession it does it.

When the truck is sitting idle I notice on the 3rd pump when the lights dim I hear something slightly buzzing in the engine bay and the RPMs dip ever so slightly.

So far to troubleshoot I got a new battery (it was about time anyway) and that did not solve it. Before I start disconnecting wires and brake lights to find a possible electrical short or grounding short can anyone try this on their Taco and see if it does it?

I did replace my taillights with factory blacked ones a while back before the LEDs were installed, but again I never noticed this behavior. Not saying it wasn't there, just never noticed.

I have heard it could be the brake booster? It apparently puts a decent load on the system when it operates? If I turn off the headlights and just turn on the front LED bar, the LED bar does not dim at all....however I also heard they are not as sensitive to load changes as the headlight bulbs are.

 

Are you sure the battery is up to all this additional load? Batteries get old and weak over time.

 

The battery is brand new. All LEDs are off when I experience this behavior so there is no extra load on the system.

Perhaps I should have clarified that better in the original post.

 

My TRD OR does this too. Completely stock with halogen headlights and a relatively new battery. I think it's probably the electronic brake booster.

I've been noticing it more these past few months, but thinking that could be because it's almost always dark when I'm driving in the winter. Also possible that my 80k mile alternator just isn't what it once was.

 

My offroad also dims a bit when I hit the brakes. My battery is old, but it lives on a battery charger at night so its 100% charged every day.

 

Mine has done it since new, usually when braking on the heavier side when coming to a stop (i.e. last second red light change). Headlights dim maybe 10% for a brief second and RPM's dip a small amount. I also assumed brake booster and haven't thought much of it since. 45k miles or so and hasn't gotten better/worse that I've noticed, I just replaced my OEM battery a few weeks ago so I'll have to pay attention if that affected things. No electrical/lighting mods.

 

Thanks all. I guess this makes me feel better that it's "normal" behavior.

 

From what I know the hydraulic pump I believe pulls 40-50 amps when it runs, mine does the same and it's done it since new. I assume it's just a slight voltage drop across the whole truck when it kicks on.