disfuncitonal tail light warning light is on due 2 led bulbs

QIK_GT4

New member
does anyone know why the warning light for a disfuncitonal tail light would light up if im using LED stop/tail lights?
 

hacker_720

New member
You have LED tail light? thats cool
I didn't know there was a warning.
It would trigger because the voltage/current/resistance is now different in the tail lights because you are using LED. I recomend measuring the stock resistance in the bulb and then matching the LED to that using some resistors.

but this is just a guss seeing how I have nver done it.
 

Mafix

New member
amperage is different, which is what i believe that thing reads. at any rate just take the bulb out of the dash.
 

Toxygene

Active member
There is another fix for this. Some people have soldered a resistor onto the bulbs or wiring to fix the resistance issue. What you could do is use a normal bulb and measure the resistance across the bulb. Then measure the LED bulbs resistance. Add a resistor to make up the difference.
 
hey guys, just reading up on the whole LED tail light conversion and the subsequent warning light on the dash coming up due to the resistance difference. there were a few reasons why i converted to LEDs; brighter nicer looking lights, and the additional benefit of drawing less current from the electrical system - i thought it might help the whole dimming characteristics our cars suffer from. I just wanted to run this by those who are more electrically inclined than I. I figured using resistors to fix the warning dash light pretty much negates the "less draw" on the system because the resistors basically bumps the draw back up. is that correct? That and i noticed the resisters get way too hot for my comfort level. Is my only recourse to pull the dash light if i don't want to use resistors? is there a relay i can pull instead of taking the dash apart? Do you think there is a substantial difference in current draw that would be of benefit or am i just picking straws?
 
so to add to my post. There is a module "lamp failure sensor" they are small squarish plastic modules (boxes) with a multipin connector in various colours from red, yellow blue, etc depending on type of Toyota. Does anyone know where this is in the celica? other toyotas have them in the trunk, on the driver side rear side panel; i've found this online on various sites. I wonder what happens if you pull the sensor? Does the light just go out, or does it effect more stuff negatively. A further thought, cracking one of these babies open we may be able to alter the resistance it dectects. So where is this module? anyone come across it?
 

WarTowels

Active member
I don't know which specific one it is, I can check my BGB when I get home or you could download the online version available on the Alltrac FTP (search for it).

But it's going to be in 1 of two places.

Either drivers side (LHD) on the left- whole crap ton of fuses there.

Or, on the passenger side by on the right. If you remove that kick panel, and the little piece that attaches to it, there are some lighting fuses there.

Goodluck! Have any pictures of the LED lights vs. regular?

-Towels
 

BlueDragon

New member
i too would like to know more about this issue, if anyone does the tests please let me know what the resistance is so i can order leds that are close enough i will not encounter this problem... if its just a warning that its actually drawing LESS current then usual im fine with that... thats the whole idea... more light less drain or loss to heat via normal filiment.
 
thinking back to basic electronics classes :) I'm pretty sure adding load resistors to trick the "lamp failure sensor" and warning light on dash negates the benefit of leds drawing less. The resistors basically bump up the draw back to traditional bulb draw (hence the stupid heat the end up producing)

if anyone thinks otherwise we'd love to hear it, but i think that's the case.

So now, short of pulling the light out of the dash, anybody have any better ideas? looking at the electrical pages of the BGB online, i think the "lamp failure sensor(relay)" is actually behind the dash instrument cluster. which makes it not any easier than pulling the light since you have to get back there anyways.

If we can alter the sensor relay that would be an option, but that's beyond my scope.

i'll try to get photos up. the brightness i think isn't that different, but the richness of the red colour is deeper/nicer and the instant on and off is a bit more noticeable. i really wanted to just create less draw on the system.
 

GT4RC

New member
Heres some questions to mix it up.

Is a voltage change directly related to the amount of electricity drawn?(amps)
Does adding a resistor add amperage drawn? or does it just adjust the voltage through resistance to trick the indicator?

Maybe look up the characteristsics and effects of a resistor on wikipedia or something, you need to find out if it increases amperage.

man this woulda been simple a few years back when i was hardcore into audio.
 
without thinking too much, i believe you can assume voltage is a constant at 12V (car) which actually varies from 11.8-13.8V but you get my drift. so really using the basic formulas, resistance is affecting the draw/load/current/ eventual wattage in relation to ohms etc etc. basically think of the resistor as another incandescent bulb drawing X amount of current.

i'm thinking more and more the whole resistor thing is crap, in terms of lowering your current draw. that leaves us with 2 options really; pull the dash light, or somehow alter the lamp failure sensor/relay.

sucks, but if you want the benefit of drawing lower current / using less wattage, that's the only way.
 

Corey

Active member
Info on the red lamp failure box: PN 89373-20160

I just discovered it in my car. I found it next to the ABS g-sensor which, on my RHD car, was mounted right above the rear passenger side System 10 speaker.
 

underscore

Well-known member
so that's what that stupid light on my dash is for. I better check my tails then (barely driven the car yet).
 
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