Thermostat blank screen / no power
A dead display is usually a missing 24 V supply, not a bad thermostat. Work from batteries and breakers to the furnace door switch, condensate float switch, board fuse and transformer. A board fuse that blows again points to a shorted thermostat or outdoor wire.
Cross-checked ~45 min moderateBrands: All
Before you start
- Turn off power at the HVAC switch or breaker before moving wires
- Inside the furnace, 120 V terminals sit near the 24 V board: measure only on the low-voltage terminal strip
- Never bypass the door, limit, rollout or condensate switches
Diagnostic steps
Unlock all 6 steps with expected values
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