Courtesy light's gone mad!! Help

CandyLS said:

Hey guys having a slight problem with my 03 LS, I just replaced all the interior lights with LEDS. Map lights, rear reading lights and the under dash lights, here's where the problem comes in and sorry if this post is long i've been fighting with my car for 4 days trying to figure this out so please bear with me. I noticed a slight problem with my rearview mirror a couple months ago, the auto dimming feature worked when it wanted to and sometimes the map lights wouldn't come on until i tapped on the mirror then the auto dim would turn on then go back off. Well after installing the leds i noticed at night they stayed dimly lit, flashing with the bass in my car, a light tap and they would shut off and come back on, wiggle the harness same issue, the next night i noticed the under dash lights were dimly lit also only because my gf was wearing white patent heels and i noticed the faint white glow, and here's where it get's weird, i put a test light on the terminal on one of the map lights and they shut off, the under dash stayed on now mind you the rear lights don't have this issue, yet, when i put the test light on one of the under dash ones one side lit up the test light with the led still being dimly lit moving it to the other side caused the led to fully light!! I took the cover off one of the rear lights and noticed when i tapped the rearview mirror they would slightly light up not as strong as the front but enough a quick tap of the mirror and they shut off, i looked to see what the issue was when the map lights came on the rear ones shut off, when the map lights shut off all the others lit up dimly, then they all started to flicker!!!! When they stopped the map lights were still dim but all the rest had shut off, i turned the lights on from the switch now the map lights don't come on at all the rest work fine, the only time i can get the map lights to work is if i turn them on from the mirror. Could a voltage leak or an open circuit in the mirror be causing all these problems????? Please help me out guys please i'm about to go mad.. Just as a note which i'm sure most of you will know i never had this problem with the regular lights seeing an LED can light up with the smallest voltage..Thanks Guys,James

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77Impala said:

Your car has a built in BCM (Body Control Module, or a car body computer) which most of the cars electrial systems go through. Many of todays cars have finicky electrical systems. LEDs draw way less currnt than standard bulbs (meaning that they also have less built in resistance), many switches in the cars control ground not power. Many of todays cars rely on a certain amount of resistance inorder for the electrical system to work correctly and when this balance is changed it causes electrical gremlins to appear.

First the easiest thing to try is put the bulbs back that were replaced, and check the behavior of the system. I believe you will find that the problems are gone at that point. And if so then here is several possible causes.
1) The LEDs bulbs resistance is way to low for the BCM to handle properly.
2) The switching system (possible from the BCM) is not grounding properly, thereby causing the LEDs to stay lit when not wanted.
3) There is a back feed from the grounding circuit, which again is a resistance problem.

You may find that if you leave a couple standard bulbs in the system that the rest of the LEDs may work fine. I would try like leaving the back map lights as standard bulbs.

Hope this helps. Kenny

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