.House took too long to heat from 60F to 68F. My Trane XV90's error code light blinks constanlty red. Do I have a problem?

I have a Trane Xr80 the prevoius owners did not leave a manual and the indicator light blinks four times in succession pauses and repeats. If anyone can tell me what this means I would greatly appreciate it. Thanks

My Trane XR80 furnace is only blowing cold air. The diagnostic light is bllinking 6 times which, I think, means the 115 volt polarity is reversed. Is this something I can fix or do I need a repairman?

Woke up to a smell of electric smoke... furnace (gas) on, but not blowing warmth into the house. I did a few things and this is what happened: 1. Heater on, fan on auto, no flow of air, the igniter wouldn't work either, smell of elictrical burn-out 2. Heater on, fan on, no flow of air, igniter...

My tenant is trying to turn the furnace on for the first time this fall. She can get the blower to blow out cold air, but not hot. I told her to turn the (digital) thermostat to "off" and to leave it off for a bit. Then to turn it to "heat". She says when she does that it just blows out cold...