First, I would say have you done any work to the car lately.
Second, I would say is to check any wires and or earthing wires that may have been disconnected whilst doing any work.
Third, i would check the fuses, for any partially blown ones.
Fourth, check the switch on the new cylinder, and the one behind the brake pedal.
Fifth, usually a dim light or one in your situation usually means a bad earth somewhere.
Sixth, I really don't have any idea at all, and with the medication that those doctors have given me means that you shouldn't really be taking advice from me.