During the winter, I noticed a burning smell coming from my vents when the heat was on. I turned heat off and I contacted the HVAC repairman. When he turned heat on, we could not duplicate burning smell. He check things out--found nothing and suggested replacing filters. Replaced filters and turned heat on. Worked fine for about four days until burning smell returned. It sounded as if the system was calling for the heat and something was humming, but no air coming through vent. Turned system off--contacted HVAC--still could not duplicate problem, so they did nothing. Suggested running fan to duplicate. Ran fan, could not duplicate.

When spring arrives, I turn on AC unit (which uses same system). It works a couple of days and really cools house. Then it stops cooling. Air is blowing but not very cool. Eventually air blower stops running. HVAC rep replaces fan blower motor.

AC system starts up, air blowing but not very cool. My system is almost five years old.

Is this problem related to my heating issue (warranty runs out this winter)?
What could be the problem with the A/C unit?

Did replacing the blower motor take care of the problem? And for the air not being very cold, the unit may need freon, I would contact the company that installed the system and get this fixed right, before your warranty has expired.