Why is my thermostat not working?

The usual culprits are four things: dead batteries, a tripped breaker or float switch, wrong settings and a bad location. A blank screen with a healthy system points to power. A working screen with no cooling points to settings or the equipment. These checks take a few minutes and need no tools.

Climate Pros Tucson is a referral service. If the checks don’t solve it, the licensed pro you’re matched with takes it from there.

What should you check first?

  1. Replace the batteries if the thermostat uses them.
  2. Set the mode to cool and the fan to auto, and set the target below the room temperature.
  3. Check the breaker for the air handler or furnace and for the outdoor unit.
  4. Check any switch on or near the indoor unit and the service switch.
  5. For a smart thermostat, check Wi-Fi and the app, and look for a pending update.
  6. Replace the filter. A very dirty one can shut a system down and look like a thermostat fault.

Why does my thermostat read hot when the room doesn’t feel hot?

Location matters. A thermostat on a west-facing wall or in a spot hit by afternoon sun can read warmer than the room, so the AC runs longer than it needs to. A thermostat near a kitchen, a supply vent or a window has the same problem. A pro can move it to an interior wall. See what temperature to set your AC to in Tucson.

What if the AC won’t start after a power flicker?

Monsoon storms bring strong winds and lightning, and a power flicker can follow. Many systems have a short delay before the compressor restarts, so wait several minutes before you decide it’s broken. If the thermostat is on, the screen works and nothing starts, check the breaker and call a pro. See AC not working after a power outage.

When do you need a pro?

Call if the screen is blank after new batteries and the breaker is on, if the thermostat clicks but nothing starts, or if the wiring looks damaged. Replacement is a job for a thermostat installation pro, especially for a smart model that needs a common wire. A smart thermostat can help with TEP time-of-use peaks.

Read repair or replace a thermostat and smart thermostat not cooling. For equipment problems see AC repair and the Tucson HVAC hub.

When the checks come up empty

Note what the screen shows and which checks you already ran. Call (520) 353-2520 and we’ll match you with a licensed local pro.