Hi,
I am fitting a VT-3 (12V) and have found that only the RHS brake light would operate if wired as per diagram. To fix it I swopped terminals 3 and 4. The brake light has to do a few things and must go onto a particular multi pin in the switch. Just to complicate things I am using a 6 to 12v inverter and isolating each system(the indicator circuit and the rest of the car) with 6v relays.ie brake switch, park lights and tail lights. I can then use 12v LED tail light/indicators and 12v LED switch-backs in the cowl lights.
Regards,
John