How-to · 3 minutes · easy
How to Replace Your Thermostat Batteries
Dying thermostat batteries cause about 20% of 'my furnace won't turn on' calls. Most thermostats run on AA or AAA batteries that last 1–2 years. Here's how to swap them.
What you'll need
- AA or AAA batteries
Steps
- 1
Pull the thermostat off the wall
Most modern thermostats slide or pop off the wall plate. Some have a small screw at the bottom. Don't yank — apply firm even pressure.
- 2
Find the battery slot
Usually on the back of the thermostat. Look for two AA or AAA batteries.
- 3
Replace with fresh batteries
Use brand-name alkaline. Lithium lasts longer in cold rooms. Match the +/- markings.
- 4
Snap the thermostat back on the wall
Make sure it seats firmly — bad seating = no contact = blank screen.
- 5
Wait 30 seconds and test
Some thermostats reboot for 30s after a battery change. After it settles, set a heating or cooling call and confirm the system responds.
When to stop and call
If the screen is still blank after fresh batteries, or the screen lights up but the system won't respond to a call, the thermostat or wiring needs attention. (416) 258-2460.
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