Condition
Heat Pump Not Turning On
Heat pump is unresponsive in heating or cooling mode. Defrost board, thermostat, or capacitor.
Possible Causes
Failed Defrost Control
A faulty board can cause the outdoor unit to freeze over in winter, blocking heat absorption.
Root Cause Analysis →Diagnostic Tests
- Check board LEDs
- Verify defrost sensor
- Test mode switching
Repair Options
Incorrect Thermostat Calibration
If the thermostat fails to sense the correct temperature, it won't signal the HVAC to run.
Root Cause Analysis →Diagnostic Tests
- Check 24V at thermostat
- Jump R to Y/G
- Verify battery
Repair Options
Blown Start Capacitor
The capacitor provides the electrical 'kick' needed to start the compressor; without it, the motor won't turn.
Root Cause Analysis →Diagnostic Tests
- Measure microfarads
- Inspect for physical damage
Repair Options