What do you mean it stays on 'dim'? There are only 2 options for the light, on or off. Sometimes some light from other bulbs shines through, especially from the normal dash illumination.

It sounds like the light only comes on when the pedal is pressed. In that case I expect that the pressure switch detects that the boost pressure is low. That could either be a faulty pressure switch, or the pump does not create a lot of pressure, or the accumulator doesn't hold the pressure. I don't expect anything wrong with relays or fuses.