Why is my thermostat blank or not working?

A blank thermostat is usually dead batteries, a tripped breaker, or a blown 3-amp fuse on the furnace control board — often caused by a clogged drain line tripping the float switch. A thermostat that runs but reads the wrong temperature is usually placement (sun, drafts) or age. Most blank screens are power problems, not a dead thermostat.

Likely causes

• Dead batteries — The #1 cause — many thermostats are battery-powered even with wires behind them.
• Tripped breaker or blown board fuse — The HVAC system lost power; the thermostat just shows it first.
• Clogged condensate drain — A float switch kills power to prevent water damage — common in humid climates.
• Failed thermostat — Unresponsive with power confirmed — electronics do die, typically after 10+ years.

What you can check yourself

• Replace the batteries first, even if it looks hardwired. Then check the HVAC breaker.
• Check the drain pan near the indoor unit: standing water means a clogged drain — clearing it may restore power.
• If you replace it yourself, photograph the wire terminals before removing the old unit, and cut breaker power first.

Typical cost

Pro thermostat replacement in Las Vegas, NV: $150–$350 for a standard programmable model installed; smart thermostats $250–$600 installed. A diagnostic visit alone runs $100–$250.

When to call a pro

Burning smell from the thermostat, visibly damaged wires, or a breaker that trips again after reset — that's an HVAC or electrician call, not a battery swap.

Get free quotes from Las Vegas, NV pros →

Data by Servik — verified local pros from official license records and public sources. Cost figures are typical ranges, not quotes; a pro's written estimate is the real number.