Saitek Switch Panel - engine knob does not work

I have a Saitek Switch Panel - all switches and gear work, but the engine knob does nothing... However, the problem is occurring only with my FS9 based aircraft.  Is there a modification that I need to make in the "aircraft.cfg", or ".air" file, or is there a particular gauge I need to bridge this apparent disconnect between my aircraft and engine start knob?.. something the FSX default aircraft have that my old FS9 aircraft do not?  I know my best solution is to get rid of the old aircraft, and that is my next move if there's no easy fix.  Thanks.