Hmmm, I never thought to consider that the instrument bulbs might trigger
it. Thanks!

JD

..... learning all the time here.  I have noticed in the past that the brass
base bulbs do tend to corrode/oxidize quickly compared to the nickel coated
bases... thanks for that Tiger

cheers

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.