Start at the thermostat
More no-heat calls than you'd think come down to the thermostat. After a summer of cooling, it may still be set to COOL, or the set temperature is below what the room already is, so the furnace never gets asked to run. Battery-powered thermostats can also go blank or act strange when the batteries get weak.
Make sure the thermostat is set to HEAT, then raise the setting a few degrees above the current room temperature and give it a few minutes. If the screen is blank or dim, put in fresh batteries. If it has a fan setting, AUTO is the normal choice for heating.
Check the furnace switch, the filter and the door
Most furnaces have a power switch nearby that looks just like a regular light switch, and it gets flipped off by accident more often than you'd guess. A badly clogged filter can also make the furnace overheat and shut itself down. And many furnaces have a safety switch behind the front panel, so if that door isn't seated all the way, the furnace won't start.
Look for the switch on the wall or the side of the furnace and make sure it's on. Pull the filter and hold it up to a light; if you can't see light through it, swap it, with the arrow pointing toward the furnace. Then press the front door firmly into place. If you find the furnace breaker tripped, don't keep resetting it. That usually means something needs a closer look, so give me a call instead of going into the electrical panel.
- The thermostat is on HEAT and set above room temperature
- The furnace power switch is on
- The filter isn't caked with dust
- The furnace front door is closed tight
If you smell gas, stop checking and get out
This is the one exception to everything above. If you smell gas (it's often described as rotten eggs), don't flip any switches, don't touch the thermostat, and don't try to work on the furnace or the gas line. Leave the house with everyone inside, then call your gas company or 911 from outside. Once the gas side is safe, I can take care of the heating side.
Make sure you have a working carbon monoxide detector near the bedrooms, and test it this week. If the simple checks above don't bring the heat back, I'll come out for a $79 diagnostic and tell you exactly what's wrong before any work starts.
