So I'm driving my daughter back to school when the bulb-out lamp flickers on the dash but does not go out completely, it glows slightly until I hit the brakes at which point it lights up fully. I figure I have a bad lamp and ignore the slight glow. After a day or so, the glow stops & it stops lighting up when I apply the brakes, but, no brake lights come on at all (all 3).

I check fuses (OK), brake switch (OK) & lamps (OK). Befuddled, I remember the glow and since I have an extra bulb-out sensor, replace it with my back-up. Voila!

I took apart the old sensor but see no obvious problems (burnt resistor, etc.). I suspect a bad transistor, anyone know what type transistors are in the sensor?