How to Check if Your Thermostat is Sending a Signal

Having a malfunctioning furnace when comfort levels drop can be an annoyance in the least and dangerous in worst case scenarios, but before you call your HVAC professional, try troubleshooting your programmable thermostat. Many times your unit may have stopped sending a signal indicating a temperature change is needed. This is a simple project that only takes a few minutes to complete.

Start With the Obvious

Ensure your wall-mounted thermostat is turned on, and that it’s set on the seasonal selection — either ‘cool’ for the warmer months or ‘heat’ for the colder. Next, make sure you have fresh batteries in the unit. The device may still seem powered, but this could only indicate the last life of your batteries. There simply might not be enough ‘juice’ to send a signal to your furnace. If you can’t recall the last time they were replaced, put fresh ones in. If your furnace still doesn’t kick on, move onto the next step.

Troubleshooting Your Thermostat Signal

First, turn off your breaker box, and remove the front panel. You’ll see two wires connected by screws or clips, labeled ‘R’ (or ‘Rh’) and ‘W.’ If the label is not there, the wires can be identified as red and white. Unfasten the two wires from the control board, and then twist them together. This bypasses the thermostat controls, and let’s you manually turn on your furnace. Power back up your breaker box, and raise the controls slightly, perhaps 5 degrees.

If the furnace kicks in, you have a faulty programmable unit and will need to replace it. These are inexpensive units, and can be purchased at your local hardware store. If, however, your furnace still doesn’t turn on, this indicates a more serious problem. Contact your HVAC specialist to schedule a diagnostic on your furnace.

For assistance replacing your programmable thermostat, or any other questions regarding HVAC issues, please contact your friendly neighborhood professionals at NisAir Air Conditioning and Heating. We’ve been serving the Martin County community since 1973.