The most likely cause is NOTHING WRONG.
I have noticed on all my fords that light creeps over into the next light very slightly, now try the same, WITHOUT your handbrake on.
The easy way to check thye alternator without a metre is to face a wall(the car) and rev the engine slightly each time the revs pick up there will be a small but disctinct increase in light brightness, other wise just measure with a multi metre if you have one.
If you look on the rear of the clocks where the bulbs go for the warning lights, you will see they are a VERY thin white section around each bulb, I did on one car paint these black inside the holder bit, and it stopped the small amount of light travel.
tabetha