On my '92 300D occasionally upon braking the burned out bulb indicator
light activates. I've had someone else hold the brake while I look for this
phantom bulb to no avail. Today it did it and on a whim, turned on my
headlights. Voila, the indicator went out. What's up?
The American and German bulbs have slightly different wattage
(resistance). The American draws a little bit more current which may
damage the delicate German electronic over long period.
Also, the way to monitor the bulb-out is by comparing the current usage,
either to a predefined value or left to right (depending on manufacturer
design). So different bulbs on the left and right may trigger the
bulb-out warning. On the other hand, no bulb-out warning in the
left-right method when BOTH are out.
I suspect JD's problem is on the tail lights. One of the bulb may have
a partial short (which changes the current) to the ground (for example,
crossing filament). When the taillights are on, diagram is corrected
and the current becomes normal.
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