ok. i broke out the meter and here is what I measured on the positive dimmer lead from the wire harness:

(voltage test)
no voltage when light switch is off
~ 12v when light switch is on

(resistance test; ground to auto chasis)

~ 3.5 on 200 ohm setting with ignition switch in off to on position (engine NOT running)
-circuit open when light switch is on

~ 130 on the 200 ohm setting when the engine is running
-circuit open when light switch is on

again, the radio does not have a connection for the dimmer lead from the harness. there is a connection for illumination, but there is a lead from the harness and it's connected to the radio.

again, thanks for any help!