How do I clean a flame sensor on a 1993 Len...

You can sand the flame sensor but it sounds like another problem. Sounds like a limit switch or something in the control circuit, You need to have a service tech look at this. Ask for free estimate on repair. I have worked on hundreds of these units and they are sometimes tricky to work on. Lenox has come up with new controls for the whisper heat furnace to replace the old ones. If the flame sensor is bad the unit will try to light a few times and lock out and you ahve to kull power to the furnace to reset. If this is whats happening clean the sensor nd you should be ok If not you need help from a service tech.Rus