Ecobee
Intermittent Low-Voltage Control Circuit Fault
Thermostat frequently displays 'Equipment offline' or 'Equipment not responding' messages
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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 thermostat wire connections, Intermittent short in thermostat cable, Weak 24V transformer, Furnace board intermittently resetting
How to Fix / Troubleshooting
Safety: Turn off power to furnace/air handler and outdoor unit before inspecting wiring.
- Step 1 – Tighten all low-voltage connections: At both thermostat and furnace board, remove and reinsert each wire, then tighten screws.
- Step 2 – Inspect cable routing: Look for thermostat cable run near sharp metal edges or compressed under drywall that could intermittently short.
- Step 3 – Monitor furnace board: Observe if the furnace control board LEDs reset or flicker when the error occurs, indicating a board or transformer issue.
- Step 4 – Replace damaged cable or transformer: If intermittent shorts or low voltage are confirmed, replace the affected cable or upgrade the transformer as needed.
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Repair Difficulty
Hard
4/5
Required Part
Thermostat Cable or 24V Transformer
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