Can i add my thoughts to this one. My bus is fitted with this light (US spec. ). I have a switch on the handbrake lever which puts the light on. It looks the same as a door pin switch. This may help.
I tried disconnecting the '61' wire at the alternator end (with the engine off) and the light stayed on. It made the alternator light dim but not go out totally so i assume theres a wiring gremlin somewhere.
Removed the stereo again and didn't find any trapped wires and no loose ones either. I did finally manage to get to the wiring on the back of the warning light and with a multimeter I get: 12V at 15 terminal (wire from fusebox) with ign on 12V at 61 terminal (wire from alternator/ign waring light) with engine running but i still get 1.15V at 61 terminal with just ign on ??? 0V at K terminal (red wire from brake light switches) with ign on and 0.35V at K terminal with ign on when brakes are pressed. I don't reckon there should be any power at the K terminal at all if the brakes are in good condition and i'm not sure about the 61 terminal though i suspect that shouldn't have any power with just the ign on either. :-
Must have just been a duff warning light as thanks to the replacement i got off Majorhangover i now have a working brake warning light.
My dad disassembled the old broken warning light and found a burnt out transistor. Replacements are pennies so he's gonna see if they are still available and solder a new one in so i can keep it as a spare. He did the same thing on my eberspachers control unit. Over £100 from espar for a second hand control unit or under £2 for all the transistors on the whole circuit board. Guess which option we chose?