Have a Trane XE 78 with a whites rodgers 50a50 furnace inside with an outside condenser. There seems to be no power to the unit but the thermostat says "cool running". Nothing wrong at the breaker box. Is there a fuse somewhere or has the unit just blown?

The AC will have a fuse, often at the furnace.

Ok- I looked but saw nothing that resembles a fuse. There is no power to the unit whatsoever. Indicator light is completely off.

I would be totally flabbergasted if there weren't a fuse for the unit. Nevertheless, you can trace the wire from the circuit panel to the unit and test for the presence of power with a test light or a meter. Are you comfortable working on that level?