Head Lights dimming when I press the brake pedal.

I was just wondering if anyone else is having this issue. I have a 2016 TRD off road tacoma 6 speed MT. I have noticed since new when I press the brake pedal there is a noticeable light electronic click/clunk in the pedal. Then the headlights noticably dim. It happens no matter what amount of pressure I apply to the brake pedal. Its not the abs kicking in because it brakes work normally. I'll be taking it to the dealer but I don't want them to tell me it's normal because it seems like it should not be dimming the lights. I have done nothing to the electrical system or lights. Its all stock other than a skid plate and grill. Thanks in advance.

 

Definitely not normal, so take it to the dealer. If they try to pull that, then find another dealership to work with. There's a warranty for a reason, so use it!

 

Check your battery connections and your alternator. Make sure nothing is loose. You shouldn't be dimming your lights when pressing the brake.

 

I don't know if it's related but I did notice that when my tuck is cold and I hold the brake pedal down the RPMs increase, release pedal and they go back down. It doesn't do it once it's warmed up. it's also a manual. If there is some type of increased engine load from the brake system that is not being compensated for in your truck(by increased RPMs) that may be why your headlights dim. Do you (or anyone else) see the RPMs go up when you hold the brake pedal down when your truck is first started?

 

Why do you need headlights to see if you are slowing down?

Just kidding, yeah sounds like something to get fixed ASAP.

 

I will pay attention to this next time I start it up and let you know.

 

I've noticed the RPM increase when applying brakes on cold starts, 10F outiside. I think I remember seeing the headlights dim slightly when I hit the brakes while it was warming up. I usually have to scrape some ice, by the time I'm done with that the truck is warmed up enough and acts normal. It's a warm 26F today, I'll see if I notice anything weird.

 

Do any of you feel a slight electronic click or clunk in the brake pedal with a manual transmission. They are trying to tell me it's normal for a manual transmission. I refuse to believe that a brand new trucks head lights should dim when you use the brakes.

 

No. No feeling of anything through the brake pedal on my Taco only the RPM increase as mentioned. I actually notice that in my 2004 4Runner and often wondered if it was normal. It feels like the ABS is kicking in for a split second but it's not and it happens when I'm not even moving. As far as what the dealer told you, I call BS. Why would it be normal for a manual and not an auto? Aren't the brake systems basically the same?

Just out of curiosity, do you have the tow package? If so, you have a higher output alternator than trucks without tow package. I have tow package on mine.

 

That's the exact feeling I was trying to describe! And yes I have the tow package and I thought the same thing it's the same brake system as the auto. They are trying to say it's when shifting the engine will bog down and the lights will flicker like on all manual transmission vehicles when the engine bogs down if you shift shitty. That's not what it is though. Its directly related to pressing the brake pedal. I refused this explanation they are on the phone with a TOYOTA electrical engineer now.

 

Well so far it's supposed to be "normal" which I doubt. I just can't see how the lights dimming can be normal operation. I'll have to try another 2016 MT to see if it does it as well.

 

^^ This is exactly how my truck behaves at cold start up.
I too feel the slight electronic click/clunk when applying the brakes. I think these two "symptoms" are directly related to the type of brake booster we have on the OR. I read in another thread that it is electric rather than vacuum, and if you look under your hood, you won't see the big assed can behind your master cylinder that is typical in a vacuum system.
As far as the lights dimming, I honestly haven't noticed that.
You just know I'll be watching for it now, thanks for that!


Frank

 

Oh great thanks that helps a lot! Let me know about your lights.

 

I'm no electrical engineer, but I've seen this happen plenty of times on vehicles, Ford in particular. Most of the time there is a ground fault somewhere.

Could be same reason for the rpm gain, additional load on the alternator is causing it to add a little speed to boost the output.

 

OK, I just checked out the headlight/brake thing - Here's the skinny:

With the truck idling (hot), the lights dim just slightly for about .5 to 1.5 seconds when depressing the brake pedal. I had the door open and was listening for a compressor/pump like sound (brake booster) and sure enough - you can just barely hear it with all the engine noise. The lights dimming and then returning to normal directly followed this sound. I also saw the same thing in the dome light ('cause I had the door open!). If you hold the brakes, the lights just dim once.. presumably because you've built up enough pressure in the brake lines etc.
Then, I killed the engine and tried it again - no brake booster this time, and thus no dimming.

To sum up, I think IMHO we're both good and our trucks are behaving normally. Either that or we have the exact same problem

Frank

 

Awesome! Thank you so much! I couldn't find another MT to try it on and that's exactly what mine does as well.

 

I drove mine this evening, and it does the same thing MOC211 described, so it's not limited to the OR. When driving, if you stay in gear when applying the brakes the alternator seems to produce enough amperage to prevent the dimming, however if you shift to neutral and then apply the brakes, the lights will dim. I agree that it is normal behavior, I'm not worried about it.

 

Anybody that's having this happen also have the screen between their dash gauges flash brighter for a second? I'm getting the exact same symptoms + brightened dash screen. Checked grounds, sanded + dialectic and it did not remedy. (Dash cluster light turned down to either zero or +2)

 

I get this increase in RPMs when it’s cold, but that’s the truck trying to warm up.

The headlights shouldn’t be dimming. That’s an electrical issue

 

You need to check your charge voltage at the battery and see what it is reading when this is happening. Low alternator output at idle is a culprit of this sort of problem.