Johnson Controls
Display Backlight Power Instability
Thermostat backlight flickers or brightness changes unexpectedly while in use.
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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 display connector, Failing LED driver circuit, Voltage fluctuations on low‑voltage supply, Firmware dimming bug
How to Fix / Troubleshooting
Safety: Turn off power to the thermostat before removing it from the wall.
- Step 1 – Check brightness settings: Ensure any auto‑dimming or motion‑based brightness features are configured as desired; disable them temporarily to test.
- Step 2 – Inspect connectors: Remove the thermostat and reseat the display ribbon cable or connector on the main PCB.
- Step 3 – Verify supply voltage: Confirm that 24 VAC between R and C is stable and within range.
- Step 4 – Replace display or thermostat: If flicker persists, the LED driver or display module is likely failing. Replace the display assembly or entire thermostat.
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Repair Difficulty
Medium
3/5
Required Part
Display Assembly / LED Driver Circuit
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