Headlights dimming when braking.

Hey, all.
My 23 OR has a headlight dimming issue. Every time I hit the brakes the headlights dim. While driving, in park, and in neutral.
19k on the odometer. This is a new issue.
I recently had the brake booster replaced. (2 months ago) now that it's dark out when I head to work I've noticed it.
I'm taking it in under a warranty repair. But I just want to make sure that this isn't normal. The truck is completely stock still.

I've read every post I could find about this subject. I didn't find any with this issue on a truck this new.
Please help. I don't want the dealership feeding me BS. This is the same dealership that replaced the master cylinder and overfilled the brake fluid reservoir...

 

Did they tap into the... headlight's to get power to the brake booster???

Do you still have brakes with the headlights off? lol.

 

I would go to a different dealership though, Your warranty is good everywhere.

Doesn't guarantee you won't have another retard working on your truck, but it's a good bed that you won't have that *specific* retard working on it.

A different dealership will be more likely to call out whatever BS the first one did, where as the first one is guaranteed to try and cover it up.

 

Typically a weak battery or charging system.

Start with checking the battery terminals, make sure they arent loose.

 

Isn’t it “common” to also have a loose ground cable?

 

Not from the factory, but you never know what techs are touching.

It doesnt hurt to check thats for sure.

 

@Bishop84 whats the chance that replacing the brake booster cut into some positive wiring sheath/insulation and is grounding out somehow when braking, causing a large power draw (but not enough to blow a fuse)?

 

Honestly I would have preferred they gave me the part to replace on my own! The Big "Now hiring service techs, will train" sign in the front of the dealership doesn't give me the best feeling, lol.

 

Bet, the word you're looking for is Bet.

 

I'll look everything over more throughly tomorrow.
The flashlight wasn't quite cutting it. The next nearest dealership is 45+ minutes away.
Thank y'all for the quick response!

 

Different dealer and I agree with lose cable.

 

Had a similar problem in my commuter car and when I replaced both brake lightbulbs the problem went away. New or not, no telling how long the lightbulbs sat on the shelf before being installed.

Also, I echo the "check for bad ground" posts above (and soon below) in this thread.

 

I took it into the original dealership again. After 8 hours in the shop, they said it has nothing wrong. Toyota said to give them a shot first then they could escalate the warranty repair to another dealer. I have an appointment with the other dealership an hour away, next week.

Now they are saying this is normal. But if I upgrade to the LED lights it will stop. [2500.00ish]
They said they checked on a comparable vehicle and it does the same thing. I asked to see it, they said that comparable vehicle was no longer in the shop...

https://youtu.be/jLruiQzGi9A?si=ggFDkMZx4dRTzLTb

 

Unplug the brake booster module and see if it still dims. When you hit the brake the booster adds a load to the electrical system in order to maintain line pressure. If your battery is crap it might be enough load to drop the voltage and cause the lights to dim.

 

^^ This ^^

 

One small thing I can point out is that if the alternator is working correctly, the battery is doing nothing except getting charged. You could disconnect the battery and nothing would change. The battery is for starting the engine and also running electrical stuff when the engine is off.