HVAC Systems · Electrical Components
Thermostat Wire & Cable
Multi-conductor low-voltage cable (commonly 18-gauge, color-coded) that carries 24V control signals between the thermostat, air handler, and outdoor unit. Conductor count (4, 5, 8-wire) determines available functions.
Common uses
Carrying 24V thermostat signals, connecting indoor and outdoor controls
Common symptoms
- Intermittent thermostat operation
- Missing function (e.g. no cooling wire)
- Corroded or broken conductors
Common repairs
- Re-pulling cable with more conductors
- Splice repair
- Terminal re-landing
Related terms
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