Applicable Systems
Carrier ComfortLink Thermostat/Controller
Symptoms
Defrost fault. The defrost cycle in heat pump mode is not operating correctly.
Possible Causes
- Defrost sensor failure
- Defrost control board or relay fault
Troubleshooting Steps
- Step 1: Check the defrost sensor resistance and wiring
Sensor is faulty or wiring is damaged - Step 2: Verify the defrost relay operation
Relay is not energizing
How to Reset
To reset: Replace the sensor or relay, then reset the controller.
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Source: Carrier HVAC Troubleshooting Guide, Carrier Corporation
Category: HVAC Residential
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