Do I NEED a reducer for the LEDs?

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Apr 29, 2017
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Orange County CA
So one of the running/brake lights in the tail hatch of my 2002 Sienna burnt out so obviously I had to get in there to replace it. A minor annoyance dealing with the trim as opposed to the more outer set of lights. Also for some time now the red of the red lens has been fading a little bit and the light was starting to drift a little more toward a pink hue as opposed to real red.

So while I was at the auto parts store getting a replacement bulb I noticed RED 7443 LEDs. Also some nice white 921s for the backup lights. So now they are all on board in all my rear running/brake and backup lights.
However, as you have probably already guessed from the title, I did not wire in voltage reducer.

The reason I did not do that is because I did not think about it until after the fact.
I had previously, for over three years now, been running LED turn signal lights in the rear and I knew something had to be wired in if I also wanted to run them simultaneously in the front. So I just stuck to the rear for those. But something regarding that and the wiring popped into my head with this job, but not until after I had it completed and all put back together.

So, did I screw up and if so what is the likely result?
I mean do the LED bulbs just get too much juice and eventually burn out much quicker or is there the possibility of any damage to my electrical system in general or just what?
Thanks in advance.
 
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Feb 6, 2021
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1,314
They probably have a voltage regulator in them. I don't think that anyone would sell led bulbs for cars without a voltage regulator. I could be wrong
 
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So one of the running/brake lights in the tail hatch of my 2002 Sienna burnt out so obviously I had to get in there to replace it. A minor annoyance dealing with the trim as opposed to the more outer set of lights. Also for some time now the red of the red lens has been fading a little bit and the light was starting to drift a little more toward a pink hue as opposed to real red.

So while I was at the auto parts store getting a replacement bulb I noticed RED 7443 LEDs. Also some nice white 921s for the backup lights. So now they are all on board in all my rear running/brake and backup lights.
However, as you have probably already guessed from the title, I did not wire in voltage reducer.

The reason I did not do that is because I did not think about it until after the fact.
I had previously, for over three years now, been running LED turn signal lights in the rear and I knew something had to be wired in if I also wanted to run them simultaneously in the front. So I just stuck to the rear for those. But something regarding that and the wiring popped into my head with this job, but not until after I had it completed and all put back together.

So, did I screw up and if so what is the likely result?
I mean do the LED bulbs just get too much juice and eventually burn out much quicker or is there the possibility of any damage to my electrical system in general or just what?
Thanks in advance.
My understanding is that the resistors are used mainly so the signals won't hyperflash (i.e. flash really quickly).

I have resistors in my front turn signals, but in only one rear turn signal, because the other one didn't seem to need it to prevent hyperflash.

I do not have resistors in the running lights or any other bulb that doesn't flash.
 
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There's several reasons you might need an extra resistor and it all depends on the setup you're dealing with.

One issue might be that the leds pass too much current, so you need a resistor in series to limit the power draw. Not an issue if you buy finished bulbs or assemblies.

Another might be that the car tries to push a small current through the bulbs when they are off to check the circuit continuity. This won't be enough to light an incandescent but it might be enough to light leds dimly. You need a resistor in parallel to fix this so the current finds a path to ground.

Another issue can be that you get errors while the lights are on because the current passed is lower than expected. Again, resistor in parallel solves this.
 

MichaelRS

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Orange County CA
There's several reasons you might need an extra resistor and it all depends on the setup you're dealing with.

One issue might be that the leds pass too much current, so you need a resistor in series to limit the power draw. Not an issue if you buy finished bulbs or assemblies.

Another might be that the car tries to push a small current through the bulbs when they are off to check the circuit continuity. This won't be enough to light an incandescent but it might be enough to light leds dimly. You need a resistor in parallel to fix this so the current finds a path to ground.

Another issue can be that you get errors while the lights are on because the current passed is lower than expected. Again, resistor in parallel solves this.
Sorry to be a rock, but I don't fully understand much of that. I mean I understand the words, obviously, and I thank you for taking the time to outline stuff which to somebody else might be very clear on the face of it, but I don't understand the significant impact of each.

For example, what's the bad thing that happens if the LED passes too much current and is it a given that it's going to pass too much current... unless it's a finished bulb or assembly. Again not knowing what those mean.

And what's the bad thing about my LEDs being dimly-lit by the car doing a continuity check of the circuit? (although i'm not sure my 1st Gen '02 Sienna is that "smart" to be doing that).

And what errors am I going to get where, because my car does not have a computer-like display screen and, depending on errors you're talking about, I don't think any of my dash idiot lights would cover that.

So I would like to understand all that better.
But beyond that, are they likely to cause any actual, permanent harm to the system?
Permanent harm being pretty much anything more severe that, if something goes wacky, simply pulling out the LED and putting in a regular incandescent won't fix it.
Thanks
 
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Sorry to be a rock, but I don't fully understand much of that. I mean I understand the words, obviously, and I thank you for taking the time to outline stuff which to somebody else might be very clear on the face of it, but I don't understand the significant impact of each.

For example, what's the bad thing that happens if the LED passes too much current and is it a given that it's going to pass too much current... unless it's a finished bulb or assembly. Again not knowing what those mean.

And what's the bad thing about my LEDs being dimly-lit by the car doing a continuity check of the circuit? (although i'm not sure my 1st Gen '02 Sienna is that "smart" to be doing that).

And what errors am I going to get where, because my car does not have a computer-like display screen and, depending on errors you're talking about, I don't think any of my dash idiot lights would cover that.

So I would like to understand all that better.
But beyond that, are they likely to cause any actual, permanent harm to the system?
Permanent harm being pretty much anything more severe that, if something goes wacky, simply pulling out the LED and putting in a regular incandescent won't fix it.
Thanks



Too much current means too much power and burning out, like using a 110V bulb in a 220V system, it'll burn very bright for a very short time and very briefly runs 4x power. If you bought a bulb, it's already made to handle the voltage and includes internal resistors if needed.

There's nothing bad about always on but dimly lit leds, except looks. Vehicles had that technology last century already so don't need a particularly smart car.

If everything is fused properly there's no risk, at worst you pop a fuse but more likely a led just burns out
 

MichaelRS

Thread starter
Joined
Apr 29, 2017
Messages
130
Location
Orange County CA
Too much current means too much power and burning out, like using a 110V bulb in a 220V system, it'll burn very bright for a very short time and very briefly runs 4x power. If you bought a bulb, it's already made to handle the voltage and includes internal resistors if needed.

There's nothing bad about always on but dimly lit leds, except looks. Vehicles had that technology last century already so don't need a particularly smart car.

If everything is fused properly there's no risk, at worst you pop a fuse but more likely a led just burns out
Thank you. Appreciate the additional input
 
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