Carrier heat_pump Error Code 13

What does 13 mean?

High limit switch has opened due to overtemperature condition in heat exchanger.

Common causes

• Restricted airflow - dirty filter
• Failed blower motor
• Blocked supply or return vents
• Heat exchanger crack
• Low refrigerant in heat pump mode

Diagnostic & testing steps

1. 1. Check and replace air filter if dirty
2. 2. Verify all supply and return vents are open and unobstructed
3. 3. Check blower motor operation - should spin freely
4. 4. Test blower motor capacitor: expected value on label ±6%
5. 5. Measure temperature rise across heat exchanger: should be 35-70°F
6. 6. Inspect heat exchanger for cracks (CO risk)

Tools required

• Multimeter
• Capacitor tester
• Thermometer
• Manometer

OEM parts & part numbers

Blower Motor, Blower Capacitor, Air Filter, Limit Switch

Part numbers: EL680-200, HC33GE234

Safety warning

⚠️ CARBON MONOXIDE RISK: Never bypass limit switch. Cracked heat exchanger is a life-threatening hazard.