Carrier Display Power Instability

Thermostat backlight flickers or display brightness changes when equipment 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

Voltage sag on 24 VAC circuit when blower or compressor starts, Loose R/C connections, Shared transformer overloaded, Internal display driver issue

How to Fix / Troubleshooting

Safety first: Turn off power before tightening wiring.

  • Step 1 – Tighten R/C terminals: At thermostat and control board, ensure R and C wires are secure.
  • Step 2 – Check transformer load: If many accessories are powered from the same transformer, consider having a technician add a dedicated transformer.
  • Step 3 – Measure voltage (advanced): With equipment starting, measure R–C voltage at the thermostat. If it drops significantly, transformer or wiring upgrades may be needed.
  • Step 4 – Replace thermostat: If supply voltage is stable but flicker persists, the thermostat display circuitry may be failing.
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Repair Difficulty

Medium 3/5

Required Part

Carrier Smart Thermostat
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