Hi Steve/Vette,
Vette has provided a clear and accurate explanation of the function and wiring of this reasonably complex circuit. Keep in mind that the ground for circuit operation is provided at each bulb and a filament burnout will eliminate ground connection for that leg of the circuit. The ground for relay within the brake/flasher relay is provided only by the units ground with power for the relay provided through terminals #4 or #8.
If I am interpreting your comments correctly, you mentioned that at the base of the steering column, you had power delivered to the green wire as well as power at BOTH green/blue and green/yellow contacts simultaneously. Additionally, you indicated moving the switch from side to side made no difference with both sides remaining powered. This indicates a fault in the trafficator circuit and either a wiring short (not likely) or switch fault.
Also, you indicated although you did have power at the 2 client connectors at the bottom of the column, power was not present at either flasher-relay terminals (4 or 8). If this is correct, you either have 2 wires burned out or non-functioning connectors at the base of the column.
With no power at terminal #4 or #8, the internal relay can not function and the switch will not take place. Additionally, you also indicated that jumping Flasher-relay terminal 1 to terminal 2 allowed the lights on the left side to illuminate and blink. With this result, and knowing your brake lights also function, you have shown that both light circuits have grounds and the flasher-relay's internal contact points are functioning properly.
To check out the relay within the flasher-relay, I would jump terminal 1 to terminal 4 (left) or 8 (right). If the left side signal lights blink when terminal 1 is jumped to terminal 4 and moved to the right side when the jumper is moved from to terminal 8, I would consider the internal relay functioning properly and the full flasher-relay working.
So, we are down to
1. A fault in the trafficator switch (delivering power to both client circuits simultaneously) and
2. NO Power being delivered from either of the client leads at the steering column to the flasher relay.
Again, some of my analysis is based on my interpretation of your presentation of your test results.
Ray(64BJ8P1)