Check batteries and settings
Replace batteries if the display is weak or blank, and confirm the mode, setpoint and schedule.
Thermostat blank, wrong, or not controlling the system?
A failed thermostat can make a working system look broken: no heat, no cooling, or a system that never shuts off. Check batteries and settings, then call 833-877-1717. RepairNowUSA connects the request. An independent HVAC technician does the repair.
Am I in the right place?Yes for a blank screen, a system that ignores the thermostat, wrong temperature readings, or one that will not shut off.
Is this urgent?More urgent in extreme heat or cold.
What do I do next?Check batteries and the breaker, then call 833-877-1717.
System itself not running: emergency AC or no heat.
RepairNowUSA editorial review · Last substantively reviewed October 14, 2026 · Review standards
Quick checks
Check the breaker and switch
Make sure the HVAC breaker is on and the service switch at the furnace or air handler is on.
Check the drain safety switch
On many systems a full condensate pan trips a float switch that cuts power to the thermostat. Water in the pan is a clue.
Wiring changes
Smart-thermostat installs on some systems need a common wire or have high-voltage connections (line-voltage thermostats). If you are unsure, leave wiring to a technician.
Common thermostat problems
Blank display
Dead batteries, a tripped breaker, a blown control fuse or a float switch can blank the thermostat.
System will not turn off
A stuck relay, wiring short or failed thermostat can keep the system running.
Wrong temperature
A thermostat in sun, near a vent or on an outside wall can read wrong. Calibration or relocation may help.
Smart thermostat problems
Some smart thermostats need a common (C) wire for steady power. Without one they may restart or lose Wi-Fi.
What to have ready when you call
- Property ZIP code and whether it is a home, rental or business
- Thermostat brand and type: basic, programmable or smart
- What happens: blank, wrong temperature, not turning on or not turning off
- Whether the thermostat was recently replaced
- Whether there is water in the drain pan
How thermostat repair usually works
- Check the system. The technician confirms the furnace, air handler and outdoor unit have power and are not locked out.
- Test the thermostat. Wiring and signals are tested to see whether the thermostat or the system is at fault.
- Fix wiring. Loose or damaged wires are repaired, and a common wire may be added for smart thermostats.
- Replace if needed. A failed thermostat is replaced and set up for the system type.
A thermostat problem can look like a broken furnace or AC. Checking the thermostat first can save an unnecessary repair.
What happens when you call RepairNowUSA
- Describe what is happening in plain words and give the property ZIP code. You do not need to know which trade to ask for.
- RepairNowUSA checks for a participating independent provider who handles thermostat and HVAC control repair in that area.
- If one is available, you are connected. The provider confirms timing, access, scope and price with you before any work.
- The provider, not RepairNowUSA, diagnoses and performs the repair.
RepairNowUSA is a referral and connection service. Provider availability and response times vary by location, time and demand, and are not guaranteed. Before you approve work, ask what was found, the price, the timing and what is not included.
Call 833-877-1717Thermostat questions
Why is my thermostat blank?
Common causes are dead batteries, a tripped breaker, a blown control fuse or a float switch shutting off power because the drain pan is full.
Why will my AC not turn off?
A stuck relay or contactor, a wiring short or a failed thermostat can keep it running. Turn off the system at the thermostat or breaker and call.
Do smart thermostats work with every system?
Not always. Some need a common wire, and some systems such as line-voltage heaters need special thermostats.
Can a bad thermostat raise energy bills?
Yes. Wrong readings or schedules can make the system run more than needed.
Can I call at night?
Yes. You can call 833-877-1717 at any time, including nights, weekends and holidays. Whether an independent provider can come out right away depends on your ZIP code, the time and provider capacity, so availability is not guaranteed.
Authoritative references
These public sources give general safety context. They do not replace an on-site evaluation, and RepairNowUSA does not perform the work.