[57corv]

Thanks for your helpful response. I was able to open the glove door past the stops and see the control that directs the air flow. Everything was fastened so I removed the arm from the controller just to see if there was something jaming the vane. I switched on the ignition and saw the arm move. I reconnected it to the vane and now everything works fine with plenty of heat on the passenger side. This happened a few years ago during the winter and later the problem went away. I assume the motor or the controller is intermittant.
Thanks for directing me to the right area. I plan to keep "Dudley" (the '97 LeSabre) for a few more years yet so I will fix everything I can. I have the factory shop manuals.