Interior light conversion to LED

[jimmybondi]

I have exchanged the sofitte- bulb from the interior / courtesy light to a LED-type light.

Everything works fine, ON is fine....OFF is fine...but if when I set to ON with open doors, I noticed that the light will glow dimishly, when the doors are closed. Almost not noticeable except in total darkness.

Measuring across it will show ~ 2.1v no matter if with old standard bulb or LED bulb or no bulb at all....

Anyone noticed this before?

[USAndretti42]

Sounds like something back feeding through the courtesy light circuit. Has anything been added to the door switches such as a lights on warning?

[jimmybondi]

Sounds like something back feeding through the courtesy light circuit. Has anything been added to the door switches such as a lights on warning?

I hooked the alarm wire to the courtesy light circuit...

[1984_lotus_esprit]

You get 2.1V with the doors closed in the dark...the original circuit is expecting a high 1000mA current type

device, so leaking a 1mA across the bulb was invisible. If you have an electronic store near your home,

place a resistor across the bulb contacts to shunt the leakage current around the LED circuit.

White LEDs need only 0.1mA at 2.9V to become fully biased for illumination.

The circuit you have should already have a dropping resistor from 12V, so that the voltage across

the actual LED element doesn't go above 3.1V.

Are the LEDs you are using have an internal resistor so that you can put 12V to them?

A resistor, say maybe 270 Ohms will shunt a bit of current, 100 Ohms even more.

The resistor's wattage will need to be 2*(14*14)/(resistor value) in watts so that it doesn't burn up or get too

hot as to melt the plastic lamp housing. A 270 Ohms resistor 2Watt might shunt the leakage current down to where

the white LEDs don't illuminate at all.

Edited March 7, 2007 by 1984_lotus_esprit

[jimmybondi]

You get 2.1V with the doors closed in the dark...the original circuit is expecting a high 1000mA current type

device, so leaking a 1mA across the bulb was invisible. If you have an electronic store near your home,

place a resistor across the bulb contacts to shunt the leakage current around the LED circuit.

White LEDs need only 0.1mA at 2.9V to become fully biased for illumination.

The circuit you have should already have a dropping resistor from 12V, so that the voltage across

the actual LED element doesn't go above 3.1V.

Are the LEDs you are using have an internal resistor so that you can put 12V to them?

A resistor, say maybe 270 Ohms will shunt a bit of current, 100 Ohms even more.

The resistor's wattage will need to be 2*(14*14)/(resistor value) in watts so that it doesn't burn up or get too

hot as to melt the plastic lamp housing. A 270 Ohms resistor 2Watt might shunt the leakage current down to where

the white LEDs don't illuminate at all.

Wow, thanks for that analysis! I am not an expert on this - so I am really impressed by the forum's knowledge.

These white LEDs were leftovers from my dashboard conversion...so I just hooked up 4 LEDs and a 560Ohms resistor to the courtesy light (somewhat scared by the news that Australia has banned the use of standard bulbs).

Anyway, I am with you that this leakage was always there, but never been noticed to to the fact that the 2.1v were insignificant for a standard bulb.

I am not worried about the dimish glimmer at night - just adds up to the exotic charisma of the car - I am just wondering if this leakage is a TADTS...

[1984_lotus_esprit]

My back recent back ground is at an automotive supplier that makes Instrument Clusters (Visteon...please don't remind me that

this company is going BK)...For each warning icon LED on new clusters, we typically put 1K resistor across each LED to swamp

leakage current to prevent it from dimly lighting the warning icon in the dark.

Yes, this is a good and very informative site...

[USAndretti42]

Why is there 2.1 V across the light with the doors closed? Aren't the door switches open contact and thus infinite resistance?

[1984_lotus_esprit]

Why is there 2.1 V across the light with the doors closed? Aren't the door switches open contact and thus infinite resistance?

Its caused by a leakage current / voltage that controls the "theater" style dimming feature

when the light dims down or fades from full 100% ON to what appears to be 99% OFF

(but really isn't 100% OFF).

Mine leaks 0.2mA or 0.0002 Amps, not much relative to all the other key off loads draining the car battery.

Its not a perfect infinite resistance, or perfect open circuit, but is more than 50,000 Ohms.

Why 2.1V? well, that can be a sense voltage by a car alarm system and/or 2.1V is 3 diode junctions,

or 1 diode and a transistor Vbe. I don't have a schematic to know exactly whats in the electrical circuit.

Edited March 17, 2007 by 1984_lotus_esprit

[USAndretti42]

Didn't realize the later cars were so sophisticated. My light is just on or off, mainly off.

[1984_lotus_esprit]

Mine stay full 100% ON after the door is shut, then fades to OFF in about 5 seconds. All it takes is a slow discharging

capacitor across a FET transistor gate...4 parts minimum...nothing fancy...I never thought too much about it since some

US luxury cars during the 1980s started to have this type of feature.

[jimmybondi]

Mine was like Trevors. But I fitted the original relay (yellow) from Lotus. It does not have that theater style dimming (or at least I never realized that it has) but just delays the light for a few seconds before going off...