Honeywell Home Intermittent Power or Firmware Instability

Thermostat randomly reboots or restarts during operation

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Loose R or C connection, Voltage dips from failing transformer, Short in thermostat cable, Firmware bug causing crashes

How to Fix / Troubleshooting

Safety: Turn off HVAC power before tightening wiring connections.

  • Check wall plate pins and wiring: Ensure the thermostat is firmly seated and that R and C wires are tightly clamped at the wall plate and furnace board.
  • Inspect transformer and fuse: Look for signs of overheating or buzzing from the 24VAC transformer. Replace if voltage is unstable.
  • Update firmware: Use the Honeywell Home app to install any available firmware updates.
  • Replace thermostat if needed: If wiring and power are stable but random reboots continue, the thermostat’s internal electronics may be failing and should be replaced.
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Repair Difficulty

Medium 3/5

Required Part

Honeywell Home Smart Thermostat Main Assembly
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