Helpful Tips from Trustco
Things to try before calling for service:
If your system has a filter, turn equipment off and check for a clog or dirty filter.
Reset all breakers or switches for equipment; remember that some systems have 2 breakers.
Turn thermostat off then on, wait 10 minutes and check if running.
Clear all debris and obstructions from equipment.
If equipment has a circuit board with status L.E.D. lights, take note of the pattern or numbers of L.E.D. blinks and consult owners manual or call Trustco Heating and Air for advice.
Make sure there are no blocked or closed air vents through out the house.
If equipment or copper line set are iced up and won't defrost themselves, turn off and defrost for 24 hours and then check items 1, 4 and 6. Call for service if problems persist. Note for heat pumps: Temporarily switch thermostat to emergency heat until problem is solved.
Consult equipment owner's manual for instructions and troubleshooting tips.