[jeffthx]

I put in LED foglights last summer, and I would occasionally notice that they would glow after the car was off (faintly, but visible). They would eventually shut off, however. Tonight, I noticed that my fogs are still glowing, hours after I shut the car off. They're far from full strength, but they're much more noticeable than they were previously.

I do have a battery charger connected to the car while it sits in the garage, so there's a chance that this is causing a weird electrical issue that is causing them to glow. Does anyone have any other thoughts about what might be causing this? Is there anything I can do to get them to shut off completely?

Thanks,
Jeff

[Billfitz]

I didn't have that problem, but mine did flicker as soon as I unlocked the car, even though the lights were not turned on, despite having ballasts and all the required coding. Adding resistors fixed it. I used 15 ohm, not the usual 6 ohm, as 6 ohm draw too much current when the lights are on, which can toast the wiring. All of my lights are LED, but only the fogs had this odd behavior.

[sspade]

Mine do this too. At first I was a touch concerned but that was months ago!

I believe it has something to do with the LED storing a bit of energy and glowing until that energy is spent.

I'm coded and have no flickering. Never had a battery issue.

I'd say you are fine.

[upsidedownfunnel]

I highly doubt this will drain your battery. An electrical load can only receive current. It cannot pull it from an open switch.

If I had to guess, there is a very small current in the electrical system from some type of sensor or ECU to check if the bulb is intact. It would do this by passing a very small test current through the lights and would warn you that the bulb was out if it didn't sense it coming back. Since LEDs are so sensitive/efficient, you will see them glow with a very small amount of voltage and current.

If you want to prevent this, you could wire in a resistor to block off that current, but that's probably not necessary. You definitely do not have to worry about draining your battery though.

[Billfitz]

Originally Posted by upsidedownfunnel

If I had to guess, there is a very small current in the electrical system from some type of sensor or ECU to check if the bulb is intact.

That's what the warm and cold checks do, but only when the ignition is on. It causes LEDs to blink every few minutes. Preventing that, and bub out warnings, is the reason for coding off the warm and cold checks.

If you want to prevent this, you could wire in a resistor to block off that current

Resistors are wired parallel to the LED, not series, to provide a resistive load similar to that of a halogen bulb. That way if the warm and cold checks have not been coded off they won't throw a bulb out warning. A parallel resistor did cure my LED fog issue, it might cure the OPs. If the OP doesn't have drive ballasts on the LEDs that might be part of the problem as well.

[upsidedownfunnel]

Originally Posted by Billfitz

That's what the warm and cold checks do, but only when the ignition is on. It causes LEDs to blink every few minutes. Preventing that, and bub out warnings, is the reason for coding off the warm and cold checks.

Resistors are wired parallel to the LED, not series, to provide a resistive load similar to that of a halogen bulb. That way if the warm and cold checks have not been coded off they won't throw a bulb out warning. A parallel resistor did cure my LED fog issue, it might cure the OPs. If the OP doesn't have drive ballasts on the LEDs that might be part of the problem as well.

The warm and cold checks are different. I've had to code those out. I have heard of glowing LEDs on cars though, though it's usually on interior LEDs. I know a bunch of people on Chevy SS forums replaced their interior lights with LEDs (they came with incandescent bulbs) and many people got glowing issues. I theorized that people who got canbus LEDs are the ones that did not experience issues since there is a resistor that might act like a bleed.