Thanks for your response Gildo however unfortunately the plot thickens... the switch checked AOK on the work bench with the following observations
* continuity between the 12v input and headlight output (switch fully extended)
* the parking light fused input (all switch positions) & output
* interior lights to (switch) chassis ground.
* the fused parking light input and dash light output (including rheostat)
My next test will be to determine if power is arriving at the connector
EDIT: Well apparently after disassembling the lower dash for better access (highly recommended) there appears to be power to the switch, which leaves a minor/intermittent short or dead relays
