GOOGLE NEST NEST LEARNING THERMOSTAT 3RD GEN Power To Rh Wire
| CONF | DIAGNOSIS | ACTION |
|---|---|---|
|
91%
CONF
|
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.
|
|
|
5%
CONF
|
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.
|
|
|
4%
CONF
|
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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DIY Repair Guide
Watch exactly how to replace the Condensate Overflow Switch.
// NOTICE:
This report is generated by an Agentic AI Engineer utilizing probabilistic modeling.
PartSniper is an automated parts recommender service. AI-generated results may not be correct. This data is not a substitute for professional engineering advice or manual inspection. Always verify part compatibility and disconnect power before any repair. PartSniper is not liable for inaccuracies, injury, or damage.