I have a Luxaire Furnace with a/c, blower motor on furnace runs but very slowly, what would cause this, units are about 9 yrs. Old, motor starts slow and stays slow

Sounds like it is getting very tired,, A little old age + high milage. does it start fast at normal speed and then slow down? If you have one you could put a clamp on amp meter on live hot wire ,to check the amp`s that it is pulling while running,your furnace tag that gives the specs on furnace usually tell what the amps are supposed to be. If it is off very much either way, less or more than what supposed to be,you might want to look at replacing before cold weather, might be running now (briefly) but its going to happen. We all get tired and worn out ,some sooner than others

You could also try seeing if there is a lot of dirt built up on the blower and fan blades or squirrel cage.