Thermostat displays H1 and indicates high indoor temperature beyond normal operating range; system may run continuously or shut down on safety.

Safety first: If the room feels excessively hot, turn off the heating system at the breaker and investigate before continuing to run it.

• Confirm actual temperature: Use a separate thermometer to verify the real room temperature. If the thermostat reading is much higher, suspect sensor or location issues.
• Check for sunlight/heat sources: If the thermostat is in direct sun or above electronics, relocate it to an interior wall away from such influences.
• Inspect HVAC operation: If the room truly is overheating, the Payne furnace or air handler may be stuck on due to a stuck relay or control board fault. Turn off power and call a technician.
• Reset thermostat: Power cycle and perform a factory reset. If H1 persists with normal room temperature, the internal sensor is likely defective and the thermostat should be replaced.