afterglow... installing an LED bulb in the dome light

I just installed and removed an LED bulb from my dome light. it draws very little power, maybe a watt or two, as opposed to 10 watts for the standard incandescent bulb. when the bulb is in the "off mode" it still glows a little from current in the circuit. i found it a little disturbing, after installing the LED, i left the car for a half hour and still saw the bulb glowing (it produces bright blue light in the "on mode" and a nice blue glow when the normal bulb is dark)

i'm just wondering if there is a little current in the circuit at all times, as it is on the same fuse as the radio, which can operate when the car is off and no key is in the ignition...

Tags: LED, dome, light

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Not sure the light and radio are on the same fuse, but the light is designed so it can be turned on at any time, off, or on when the doors are opened
Mine does the same thing. There must be some residural current in the circuit.


RallyRedY2KX said:
Mine does the same thing. There must be some residural current in the circuit.

that's what i was thinking, i have the alarm, which also draws a bit of current. i was just wondering if somebody had a VOM and could check to see if the dome was passing a little current 24/7. maybe i'll buy a meter just to check it out (more mindless consumption, but i think my dad might have one laying around) currently, i leave the smart for 7-8 days at a time for vacations and it starts right up. my next vacation will only be 5 days next april. i'll ask my dad next week if he has a meter and i'll check the circuit myself.

having a pure, my car was delivered without a radio, i installed a pioneer, then a few months later, i got a radio #10 from e-bay. that will play for 30 minutes after it is turned on with the car ignition switched off (another "smart" feature).


Richard Baker said:
Not sure the light and radio are on the same fuse, but the light is designed so it can be turned on at any time, off, or on when the doors are opened

the radio and dome light are on the same circuit/fuse (#15) trust me! i was removing the dome bulb, not following the owners' manual (unplug the wires first!) the bulb will short out and blow fuse #15 if the wires are not unplugged first, and the radio will not play again until fuse #15 is replaced. at least they warn you in the owners manual about the dome light, if anyone ever reads owners manuals anymore...
I have an LED dome light and have the dreaded "dome glow". I REALLY dont like that because it attracts unwanted attention to the car at night. The fact that I want it to turn OFF and not just partially when I leave the car or am driving about is perhaps too much to ask? How annoying is it to have a light that wont turn off!
Add me to the List....<:-((


SATO said:
I have an LED dome light and have the dreaded "dome glow". I REALLY dont like that because it attracts unwanted attention to the car at night. The fact that I want it to turn OFF and not just partially when I leave the car or am driving about is perhaps too much to ask? How annoying is it to have a light that wont turn off!

thanks guys for verifying this, i'll pop the cool blue LED in there, for others, unplug the lead to the socket first, by design, the bulb will short out and blow ur radio fuse (#15), i bought a bulk load of fuses just in case!
I noticed the glow as well when I initially installed the LED, but was not overly concerned, because it is very minimal current. I also added footwell lighting and trunk light leds on the same circuit. As I was looking at it the other day it seems to have stopped drawing a current/it isn't glowing anymore. I certainly think the wiring in the smart is a little skimpy for my taste. I know that there is an article on evilution.co.uk about installing a beefier battery ground, which may improve the situation. Btw: When I installed the dome bulb it did not short out my fuse, even though I did not disconnect it and I do believe I might have installed it with wrong polarity at first).
i think the added lighting to the same circuit created enough drain to dim the dome LED, i'd still like to take a VOM to that circuit and see what it's getting when the car is off.

toes said:
I noticed the glow as well when I initially installed the LED, but was not overly concerned, because it is very minimal current. I also added footwell lighting and trunk light leds on the same circuit. As I was looking at it the other day it seems to have stopped drawing a current/it isn't glowing anymore. I certainly think the wiring in the smart is a little skimpy for my taste. I know that there is an article on evilution.co.uk about installing a beefier battery ground, which may improve the situation. Btw: When I installed the dome bulb it did not short out my fuse, even though I did not disconnect it and I do believe I might have installed it with wrong polarity at first).

I installed 5 led lights over the trunk and wired them into the dome switch, no glow. Shutting the door the leds dim and then go out while the incandescent goes out right away, this happens to be inherent to led bulbs.

The soft on/off circuit that's made to operate a filament bulb is leaking.  They, probably, all are a few milliamps to operate the low-level electronics through the bulb, which won't be enough to make a filament glow.  An LED will glow on a whisper of current.  The series power transistor is leaking that current.  These computer cars run all the time, eventually draining the battery to ruin it, left in an airport parking lot for a month, for instance.  Its design isn't as "smart" as the brochures sell.  The radio is running all the time, too.  That push button power switch pulses an ever-draining circuit that runs all the time looking for the button press to turn the rest of the radio on.  Everything in your house with a remote control or other press button to ON is running all the time, too.

No, they aren't.  An LED can be "pulsed" on and completely off hundreds of millions of times per second.  That's how fiber optic data is transmitted!  There is nothing in an led that "afterglows" like a flourescent light.  It's not true.  If you move your eyes rapidly around while looking at any LED tail lights, you'll see that the dimmed light isn't dimmed, it's pulsing too fast to see looking at it, an optical illusion like TV because of your eyes' persistence.  The wider the on-time of the pulse, the brighter it looks.  They all go completely dark the instant the power is removed by the pulsing circuitry.



Art Whittaker said:

I installed 5 led lights over the trunk and wired them into the dome switch, no glow. Shutting the door the leds dim and then go out while the incandescent goes out right away, this happens to be inherent to led bulbs.

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