What is happening?
Likely causes
Stop and get help: if you smell gas (rotten eggs), leave the home and call your gas utility or 911 from outside. If a carbon monoxide alarm sounds, get everyone into fresh air and call 911. Never open furnace burner compartments or electrical panels inside HVAC equipment.
Why we start with the basics
Many no-cool and no-heat calls turn out to be a thermostat setting, a tripped breaker, a clogged filter or a full condensate pan. Checking these first can save you a service fee, and if they are fine you can tell the technician exactly what you have already ruled out.
