H9's.....dimming when I hit the brakes

Anyone else notice this or have an explanation?

I touch the brakes and notice my low beams dim for a second.....then back to normal.

 

Is this new? Or, has it been that way since you got the H9's?

 

I completed the H9 conversion about a year ago. I haven't noticed any difference in the H9 light output when driving or braking. The light output from H9 is consistent in all driving conditions.

Did you replace the H9's recently? Do both H9 bulbs dim when you apply the brakes or just 1 bulb? How are they when you're parked and idling? What happens when you're in Park and press the brake pedal - Do they dim? Maybe it could be dirty contacts? Try removing the bulbs and cleaning the contacts might help?

 

Maybe because H9 needs more current (10w more on each bulb) than H11 and there's not enough current? That is almost 1amp extra per each bulb right?
If you have any additional current consuming items like a sub or something maybe the alternator +battery does not have enough juice to power on a spike?


Maybe when you trim the tabs they now not tighten properly and when you brake they shake a little that causes the light projection to change and eyes think it's dim?

(Just putting some theories since I don't have H9s)

 

the h9 will show slight fluctuations in current very easily as it pulls more than your typical bulb. i've ran h9 bulbs in previous vehicles and experienced the same thing.

 

Seems like there’s no free lunch when upgrading the headlights on our vehicles.

 

I just got in my 2018, turned on the H9 low beams and hit the brakes. 4Runner ignition off. Absolutely no dimming of the headlights.
Suspect your battery, cables, ground connections, headlight wiring, headlight connectors. Maybe a fault in the brake lights or wiring, water or moisture in there?
Put in your old OEM bulbs and compare. A extra ~2 amp load from H9s shouldn’t choke your battery or alternator.

Many years ago I heard a story similar to this. The guy had done a lot of electrical wiring mods and every time he hit the brakes he pinched a wire behind the pedal, causing a low resistance path to ground and dimming his lights.

 

Thanks for the replies everyone.

I haven't noticed it before so maybe it's new or maybe I just haven't noticed it until now.

H9's have been in there a couple of years. I did recently replace my high beams with 9011's and fog lights with H8's, but those were off and the H9's would still slightly dim when pressing the brake. It happened while diving and while parked.

Haven't gotten outside the truck to see if it's one bulb in particular. I will do that next as well as start checking connections.

Thanks all

 

Is you battery original? I've heard of Toyota's newer batteries only lasting a few years. It could be worth having it tested.

I have ~68K miles on my '19 and lately it sounds like the battery is struggling more to start it. I keep meaning to get it tested, but it's been a busy month.

 

It’s possible that newer cars are more sensitive to a weak battery. In the old days, the main tell tell sign of a weak battery was the sound of the starter.

I think newer vehicles need a strong battery and good ground circuits to behave properly. Or else the gremlins come out.

 

Good call. Yes, it is original (61,000 miles) and sounds like it has been struggling with colder starts lately.

I recently moved to the forest and installed an anti-rodent device that uses lights and clicks to (supposedly) repel rodents. I know many say this doesn't work. My neighbor who has lived here for 44 years and is a truck mechanic swears by them, so I gave it a go. It draws from the battery and is supposed to turn off at a certain point. Perhaps it's draining my battery too far??

Any suggestions on a solid battery that won't break the bank?

 

I wish I could help you there. I have been wanting to replace mine with an AGM, but I get mixed information about whether our charging system can properly charge them. I was eyeing up the house brand AGM from O'Reilly auto, as I had heard they were a rebadged version of another top brand.

Last time I put a battery in a Toyota I went to a dealer and got their brand. Now that the OEM batteries seem to be getting all of this bad press, I'm lost.

The OEM battery in my '03 was a Panasonic, and it lasted something like 10 years and 170K miles. I doubt I'll ever get that lucky again!

 

Thanks to this video my battery choices got lot more harder -
https://youtu.be/h7rTcBanpMk

 

No issues at all with my H9s, for what that’s worth. Been running them more than a year, about 11-12k miles.

agree the battery could be a problem. Mine died after the car sat a few days. Was even garaged. Didn’t leave any cabin lights on or anything. I suspect that a) the OEM batteries suck and b) there’s a drain from all the unnecessary Remote Services and / or active safety tech. I’m not confident that Toyota has implemented these things well.

 

A three year lifespan for a battery in a hot climate is not unusual. I use a battery tender on mine occasionally to try to keep it healthy as long as possible.

When my batteries start getting questionable I buy a new one at Costco. $99 for a 3 year warranty regular flooded battery.

Test your battery with a voltmeter at no load and no charging, after letting it sit 6 hours or first thing in the morning. This will give you a good idea of its state-of-charge, it’s general health.

 

You'll get a billion different answers. So ill chuck one in..
North Star has done me ok, and ive bought several agm's. From XS-Power (i was actually sponsored by them for a few years in my car audio days,.tell Scottie hey for me) to many others.
Just another option, and most wont be wrong at all..
Edit-

 

Could you explain the setup that you show here? Is that a fusible link? I can’t really tell from the pic but it looks like the +12V is exposed and very close to the body metal. Any concern with that?

 

Dual battery set up. Look closer.
And fused, both ways. Yes.

 

I had '04 with the Panasonic battery - I had over 200K and 12 years on the original battery - They evidently don't make them like they used to.

 

Are our stock batteries flooded lead acid?

 

Yes

 

I just noticed that my interior lights dim for a second when I press the brakes as well…..so not exclusively an H9 issue. Makes a good case for my battery being the culprit, no?

 

Either that, or a bad connection somewhere.