My Trane Air Handler/Heat Pump inside fan is not working... Outside compressor is running. Yesterday, I found the circuit breaker on the inside unit had tripped. I flipped it back and immediately fan started running... No more trouble until this morning. I thought I just needed to flip the breaker again... But this time breaker wasn't tripped... I flipped it off and back on. It didn't work... Still inside fan is not running. December 2009 I had a repair to this 1993 system and was told not to spend any more money to repair it. BUT... I really need to postpone getting a new system right now. Can any experts here give me some ideas about what may be the trouble?

Sounds like a possible bad motor. IF the breaker to the inside unit were tripped, the outside unit should not be running. I would have the motor and capacitor in the inside unit checked. See what repairs would cost vs replacement of complete unit. Sometimes it hurts to dump money into an old unit, but if it's a simple fix, just as well go for it.