TP-Link Kasa
Unstable Low-Voltage Power Supply
Thermostat powers on but frequently reboots or flickers
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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 at thermostat, Undersized or failing 24V transformer, Shared C wire with other high-load accessories, Intermittent short in thermostat cable
How to Fix / Troubleshooting
Safety: Turn off HVAC power before handling wiring.
- Tighten connections: At both thermostat and furnace board, tighten R and C terminal screws and ensure wires are fully inserted.
- Inspect cable: Look for damage, kinks, or crushed sections in the thermostat cable that could cause intermittent shorts.
- Remove extra loads: Temporarily disconnect non-essential 24V accessories (humidifier, UV light relays) from the C and R circuits to see if stability improves.
- Transformer capacity: If multiple devices share the 24V transformer, have a technician verify its VA rating and replace with a higher-capacity transformer if needed.
- Replace thermostat: If power is stable and wiring is good but reboots continue, the thermostat’s internal power regulator may be failing.
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Repair Difficulty
Hard
4/5
Required Part
24V Transformer / Thermostat Power Regulation Circuit
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