1. Check to see if the thermostat is actually calling for heat.
Is it set to the heat mode and turned up far enough to activate the need for heat? This may seem obvious, but many times a service call has been scheduled, only to find that the system was simply in off mode.
2. If the thermostat uses batteries, be sure they’re installed and fully charged.
It’s a good practice to replace them every heating season, just so you don’t have any surprises.
3. Check for power to the furnace.
Is the switch on? Check the electrical panel to make sure the fuse is intact or circuit breaker is engaged. If you have air conditioning, an easy way to verify that power is getting to the furnace is to turn on the fan at the thermostat. If the fan starts, then you know you have power to both the furnace and the thermostat.
4. Take a look at the filter.
A dirty or plugged filter can result in low heat (as opposed to no heat), which means the furnace runs, but not long enough to heat the house to the desired temperature. If not changed, a plugged filter can lead to a no heat failure that does require professional correction.
5. Sometimes a furnace can go into “lockout” due to an external problem.
A power outage, a brownout (low voltage), low gas pressure, or even high winds can cause the furnace to go into this fail-safe condition. You can turn off the furnace at either the thermostat or the main power switch and turn it back on to reset the lockout. Just keep in mind that lockouts can also be due to internal problems that require a professional to troubleshoot and repair. So, if resetting works, that’s great! But if the situation persists, it’s time to call a technician.
6. Check for obstructions.
If the furnace is trying to start — it’s making some operating sounds but not providing any heat — there could be lint, dander, bugs, or other obstructions in the burner compartment. If you’re comfortable taking off some panels to get inside the furnace (with the power off, of course), you can vacuum out the burner area to see if that takes care of the problem.
If you’ve tried all six steps and still don’t have heat, it’s definitely time to call your heating professional. And for the future, you may want to schedule a regular maintenance check-up, because it’s been shown that most no heat service calls are preventable with regular maintenance. ( Still have questions? Check out this additional blog.)