Bryant Voltage Drop / Power Instability at Thermostat

Thermostat frequently reboots or flickers when heating or cooling starts.

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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

Undersized or long thermostat cable causing voltage drop, Shared transformer overloaded by multiple accessories, Loose R or C connections at control board, Intermittent short in thermostat wiring

How to Fix / Troubleshooting

Safety first: Turn off power to the indoor unit at the breaker before inspecting wiring.

Steps to troubleshoot:

  • 1. Inspect R and C connections: Tighten all low-voltage terminal screws at the indoor control board and thermostat wall plate.
  • 2. Check for damaged cable: Look for pinched, stapled, or spliced thermostat wiring. Replace damaged sections.
  • 3. Reduce load on transformer: If many accessories (humidifier, dehumidifier, IAQ devices) share the 24V transformer, a technician may need to add a separate transformer or upgrade.
  • 4. Technician voltage test: Have a technician measure voltage at R and C during equipment startup. If it drops significantly, wiring or transformer capacity must be addressed.
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Repair Difficulty

Hard 4/5

Required Part

Bryant Furnace/Air Handler 24V Transformer
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