What's in the workshop this week, Pelikanblau edition

[tc4332]

I like the theory that Mark and MJ have come up with, but could be a bugger to locate.
Back to the old fashioned way, cut the cct. in half, then in half again following the symptom.
Offhand, do either of you know what the resistance is on a working car?
To my mind only 6 ohms could be, like Mark said, dragging the voltage level down to a point that triggers the action.
Again it would take a lot of bulbs in parallel to drop the overall resitance down to 6 ohms.
Good luck with this one Micheala