De-Mystifying installing and upgrading auto headlights to LEDs. What is the CANbus decoder?

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Minister of Fire
Hearth Supporter
Feb 1, 2010
Salem NH
When the low beam halogen lights in our 2007 Camry were replaced before we purchased the car, only the bad one was replaced so one light was always brighter than the other! LOL
It seemed more obvious after the lenses were polished. See
So I decided to just replace all 4 lamps with LEDs
I found the prices were better OnLine than in the local shops so I got all 4 for $49.95 made by Shenkenuo
H11 are the Low Beam Camry replacements
9005 are the High Beam replacements
Amazon product ASIN B0B7MS19G3So I plugged them in and nothing! Lol
Se that led to the question why?
Then I realized that being 12vdc the polarity was wrong and unplugged them and flipped it over and plugged them back in and they worked! Now more questions?
Why do they have a wire and black box and not compact like the halogens?
Well it could be the CAN bus decoder and or the resister kit?
Does anyone know for sure? No mention of it on the box?

Looks like the lesson here is to purchase an LED kit made for the year make and model of your car. This assures that the black box electronic module has the right components for your car!
See vid

Pic 1 - old and newer halogen headlight bulbs
Pic 2-3 new LEDs
Pic 4 LED vs Halogen
Pic 5 - they work!

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Voltage drop in the box also, provides some resisitance so the computer knows they are on.On some of the newer cars if turning with the directional signal engaed the headlamp on that side goes dim. Best Idea they came up with as some of headlights are so bright you can't see the blnker..
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I wonder if the black box is a voltage regulator they do it want to get hot? The LEDs may not want 12 v. Moving what ever is I the black box away from the heat sink makes it last longer and or cheaper to manufacture. Just my guess.
LEDs require a current limiter similar to a fluorescent tube ballast only for DC. Otherwise the LED current can vary widely with slight voltage fluctuations leading to flickering and potentially burning out the LED. I bet that's what's in the box. It is separated from the bulb due to space limitations.
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Somehow doubt that the LEDs communicate directly on the CAN bus through the headlight wiring.

Edit: I see my knowledge of these things is out of date. Disregard
yes on the current/ voltage stabilize function. couple resistors and capacitor. resistors drop voltage , cap smooths out the spikes/ripples might be a current limiting diode in there as well. Been awhile since i dealt with electronics on a daily basis. on cars everything has power supplied constantly on one side of item, computer/modules control ground connection - this all happens above the frame ground. most of the modules are bilateral reporting units besides on the same line- multiplexing. Computer sees potenial drop/rise across a particular item within a particular range anything outside of that range raises a flag. ok my head hurts now back to my simple machine tools
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If you drive after dark, and upgrade the halogen headlights to LED it seems to make a huge difference?! They are brighter than the street lights. The high beams make it look like daylight!
See pics of our Camry we just upgraded!!
1 = low beam
2 = Hi beam !!

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Looks like there is some shadowing on the left side of the low beam. I'm not a fan of these retrofits unless they are model and year specific. The headlights should be aimed and focused so as to not blind the oncoming driver. This is a common problem with retrofits.
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Yeah I'm not a fan of LEDs, the don't have a point source kinda like a halogen filament and scatter light everywhere. HIDs can be better in this regard if setup correctly.
I've held off changing our van's halogens for this reason. Factory-designed LED headlamps seem to work ok. The reflector and lens design all have to work together. Our Volt's have a sharp cutoff that is below the oncoming driver's eyes.
Funny thing with Led head lights they are bright enough but the go just so far and then it looks like a black wall. vs incadesant which kinda taper off at extended range. Might look that way because of the intensity. You do need the adapters in the circuit , voltage amperage regulation and the computer controls the on/ off, high or auto dim when climbing hills. Nothing on the new cars is direct wired , all goes through various modules controlled by the main frame. ( pia when problems arise)
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