GOOGLE NEST NEST LEARNING THERMOSTAT 3RD GEN Power To Rh Wire
| CONF | DIAGNOSIS | PART MATCH | ACTION |
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91%
CONF
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Condensate Overflow Switch
This switch is a safety interlock installed in the HVAC drain line or drip pan. When a drainage blockage occurs, water level rise mechanically lifts a float, opening the electrical contacts and breaking the 24VAC path to the Rh wire. This protects the structure from water damage but results in a total loss of power detection at the thermostat.
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CHECK PRICE | |
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5%
CONF
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HVAC Control Board Fuse
A 3-amp or 5-amp automotive-style fuse is located on the furnace/air handler control board to protect the transformer from overcurrent. If a thermostat wire shorts to the chassis or another terminal during a cycle, the fuse filament melts, instantly severing the Rh power supply to the thermostat.
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CHECK PRICE |
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4%
CONF
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HVAC Air Filter (High-Flow)
A heavily restricted air filter reduces airflow across the evaporator coil, causing the refrigerant temperature to drop below the dew point and freeze the coil. As the ice melts or the system triggers a freeze-stat, the resulting excessive moisture can overwhelm the drain system, triggering the float switch and cutting Rh power.
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CHECK PRICE |
DIY Repair Guide
Watch exactly how to replace the Condensate Overflow Switch.