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LED car lighting problem! Answered

I put some LED's in car, connected them to door sensors, but ~2V still flowing trough when door is closed (I think because sensors are grounded to frame) and LED's stay barely lit. So I need something to stop current. What would be my best option?



7 years ago

How did you wire the LEDs ??
A car has live plus DC and turns things ON by grounding them !

I found outputs (or inputs?) going from the fuse box to interior lighting. I wired them in series using 100 ohm resistor in front. I think maybe i should use voltage regulator. Could that help? I actually took a closer look at door switches, that as you said works by grounding, but it seems that they aren't really designed to be fully open.

I am assuming white LEDs although car buffs are a many colored group.

The immediate temporary solution is to put two or three !N4001 diodes
in series with the LED the diodes and will "stop" some current as you say
when you want the led (OFF) and will also reduce the (ON) current,
which you should have used a 470 ohm resistor.

The 100 ohm is pushing a harmful 100+ma through the LED, unless you
are using the Super Power LEDs.

The wiring still needs to be addressed as your regular lights do not glow.


Thanks for advice, I will try that out. The LED's are connected 4 in series with 22 ohm resistor. I was thinking about my other project parallel to this and accidentally wrote 100.

Very good 4 in series but WHAT Color ??
Needed to do the math.


5 mm blue LED's typical 3.3 V

Sorry, the four LEDs in series 3.3 x 4 = 13.2 VDC and 22 ohms or
the extra diodes 1N4001 will NOT Work !
Something must be faulted the wiring or a component.

Here is a picture of 3 LEDs in series with a resistor flowing 15 ma
through a door switch to frame ground.      A


Do you have an alarm system. Some systems use the door switches to monitor the car and may be a closed loop alarm and have current flowing continually.

My guess is similar to the alarm -- the car is monitoring if the lights are burnt out.

Are any of the existing car lights LED? Do they have a control driver board that is powered off that 2ish volts and only turns on the lights when its 12v?

No its a 1992. car. So back then they were using Incandescent light bulbs (I think they are cold in english). And I haven't found any control board.

Hmm...and they have 2v going to them at all times, even when off?

I can only think that's a bulb burnt out detection circuit then...

No car doesn't have any alarm system, but maybe central locking works that way. If its so turning it of isn't an option because back doors doesn't have any manual switches.