h0rn3t920

I put led's in all of my dome lights and they look great. but they stay dimly lit when the car is off and do not shut off. they are very dim but all the leds stay on. does this drain my battery or do they just glow due to the little amount of current they need to run?

Television

I would have said that the drain would be too low to worry about

E420SportGT

LEDs use less power than conventional bulbs...

sosh

Yes, eventually they will drain the battery like any other sort of current draw. The questios should be why do they stay on, this is not normal and why did you use leds in a dome light as they do not produce enough light to be useful.

n42w88

Are you absolutely sure that they never turn off? Do them dim and brighten just like the original bulbs did?

The R-C (resistor-capacitor) time constant may be in play here. I'm just wondering if there is a capacitor in the box that controls the interior lights, and maybe because of the much lower current draw of the LED lamps compared to the incandescent lamps, the capacitor is taking much longer to discharge - what I mean is that it's possible that the power going to the LEDs when they should be off is coming from a capacitor in the circuit rather than from the battery. This would not result in any additional drain on the battery - the same amount of power is being used, just more slowly over a longer period of time. Normally the incandescent light bulbs would draw so much current that the capacitor would discharge completely in a few seconds - the LEDs draw less current so it takes longer to discharge the capacitor.

It's just a theory.

If you leave your car overnight and the lights are still on dimly in the morning (without triggering them to come back on, of course), then there is something wrong, but if the LEDs do eventually turn off after an hour or two then there may not be any problem.

h0rn3t920

i figured out if u keep a normal filament bulb in one of the dome light sockets, the lights will not stay on dimly. now if they are all leds, they will never go off. im thinking of getting a resistor and putting it in. what type of resistor would i neeed?

n42w88

Current (Amps) = Power (Watts) divided by Voltage (V)
Resistance (Ohms) = Voltage divided by Amps

If you want a resistor that would simulate a 1/4 Watt light bulb, you'd want a 760 Ohm 1/4W resistor - they may not sell that exact value, but anything reasonably close will work. That's based on the supply voltage being 13.8V, which is the nominal voltage on a car with the engine running. If the voltage were actually 12V, a 600 Ohm 1/4W resistor would work. So, if you pick up a resistor somewhere in the range of 600-800 Ohms that should work as an around 1/4 Watt load.

You need to buy a resistor that is rated for 1/4 W - they sell them in lower wattages like 1/8 Watt, but the wattage rating is important as all the power that the resistor consumes is turned directly into heat, and you don't want the resistor to burn out or catch fire.

You may want to first try a 1/8W load, which would use a much smaller (physical size wise) resistor. That would be a 1/8 W resistor somewhere around 1100 to 1500 Ohms.

Hope that helps.

h0rn3t920

well i have tried a 25ohm 25 watt resistor, it worked, but when the lights are on it gets really hot

n42w88

A 25 Ohm resistor is too low of a resistance. Using a lower value resistor (lower Ohms) than what's indicated by the calculations will result in things getting hot, possibly dangerously hot. That's why we use equations like Ohms Law to size electrical components.

In engineering terms a 25 Ohm resistor connected to a 12V supply is considered an electric heater.

Try a 1K Ohm resistor, 1/4 W., or one of the resistors I recommended in my earlier post. Radio Shack should have one of them in their tiny assortment of electronic components.

Sorry it took me so long to check back. I've been busy recovering from lifting something up that was way too heavy.

Zigger21

I also have the same problem but my problem is located on my stop light LED. I went out nto the garage ine night and noticed my stop light LED's were dimly lit which drains the battery. Would a resistor cure this problem or will I need to back to the incodescent light bulb?

Zigger21

I just ordered a 2 x 6 OHM 50W SMD/LED LOAD RESISTORS ERROR CODE/BULB OUT/ for my front light LED turn signal and I put in brand new all Led Tail lights and when I have everything connected with out the reistors I have haper flash and my tail lights flash but I dont have any driving lights or stop lights. But when I unplug the Turn sigal connector on my rear tail light my Driving lights and stop lights will not work. But they work if I disconnect my turn signal lights. So Im going to instal resistors onto my front light LED turn signals and I hope that clears up the hyper flash and cures my tail lights problem also since they are all tied into one another. I got the 6 ohm 50 wat resistor so it will take away the front hyper flash but a I am worried I might need to put resistors on my LED tail lights also. The rear tail lights are LED for drive, Turn, and stop lights but it has an incondescent light for reverse lights.

Whitey

h0rn3t920, I've had LEDs in my dome lights for years without any problems. They weren't even the LED bulbs that you can get nowadays. What kind LED's are you using anyway?

In all these years, the only time the dome lights stayed on after the car has been switched off was when there was a short in the system (caused by a cut in the wires that tap power off the dome lights for the puddle lights, so completely unrelated to the LEDs). I sorted the short and it functioned properly ever since (must have been over 6 years now).

Given that the lights turn themselves off normally with the regular bulbs, it maybe the bulbs are causing the short. I would explore that first, rather than mess around with resistors. You don't need resistors for LED'd dome lights and yes, they do get pretty hot.....