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That is a common failure resulting in a lot more draw than you might expect. The "timer" is fed from the dome/door light circuit. When it is energized it charges a capacitor . When the circuit is de-powered, the capacitor discharges into the ignition ring light until it is done. This is what provides the timed illumination. The most common failure mode results in continuous power to the ignition ring light. I have replaced several of these over the years in different '80s. I still remember how surprised I was on the first one when I realized that all the draw was from that itty bitty little light!
Mark...
It's not actually quite like that... The capacitor is used as part of the timing, the transistor (and leaking zener) are what control power to the ring. Read my write up in the link further up and it explains a little about the circuit and the actual failure (the zener).
cheers,
george.