The thermostat instructs the heater on how to function. You set a temperature, the thermostat sends a signal, and the heater responds.

• If you’re using a heat pump, make sure that it’s set to heating mode. As simple as it sounds, it’s easily forgotten.
• Check that the thermostat is set to “auto” instead of “fan mode.” Fan mode means that the blower fan will continually blow regardless if the furnace is generating heated air. That could explain why it feels like cold air is coming out of your vents.
• The “hold” setting is used to lock the temperature in place, in the event that you’re trying to use the thermostat outside of its normal programmed settings. Whether you’re forgetting to use the hold setting or if you’ve forgotten to undo it, it can cause some confusion in operating the thermostat.

• Programmable thermostats use batteries to save schedules and perform other functions. Try replacing the batteries.
• The sensors may become inaccurate if they’ve collected dust or dirt. Gently wipe them off and see if performance improves.
• Perhaps your thermostat is tripping the circuit breaker for some reason. Check the circuit panel to find out.
• If none of the above helps, then you might have an issue with the wiring. We don’t suggest trying to fix this on your own, as working with electricity can always be dangerous.

• If it’s been more than 10 years, or if your thermostat still uses a slide or dial instead of a digital display, it’s definitely time for a replacement.
• Have another HVAC contractor give you a second opinion on the location of your thermostat. If it’s too close to a warm area like the kitchen—or in a place that’s cold and doesn’t reflect the average temperature of the home—then it might not be recording temperatures accurately.