CARRIER AC E4 Error Code 🔧 Inverter & Non-Inverter | Meaning, Causes and Easy Fix!
In this video, we explain in detail the E4 error code in Carrier air conditioners, its most common causes, and the correct steps to diagnose and fix the problem. Although the meaning of the E4 code can vary slightly depending on the model, this guide will help you understand the fault in both inverter and non-inverter Carrier systems, allowing you to perform accurate troubleshooting without immediately calling technical service.
The E4 error is commonly related to temperature sensor failures, incorrect readings, safety switches, or abnormal temperature conditions inside the system. Understanding how each component works is essential for restoring proper operation and preventing long-term damage to the air conditioner.
🔧 What You Will Learn in This Video
What the E4 error code means in different Carrier models
Differences between inverter and non-inverter units
The role of indoor and outdoor temperature sensors
Why sensor faults trigger the E4 protection mode
How to test sensors using a digital multimeter
When the E4 code is caused by the compressor thermal switch
How to perform a full reset and initial inspection
Step-by-step guidance to identify the exact fault
🌡️ Main Causes of the E4 Error in Carrier AC Units
For Non-Inverter (Conventional) Units
Non-inverter Carrier systems usually use:
1 indoor ambient (room) temperature sensor
1 evaporator pipe or coil temperature sensor
1 compressor thermal switch
If any of these components fails or provides incorrect readings, the control board activates the E4 protection code.
Common causes include:
✔ Faulty or uncalibrated temperature sensors
✔ Dirty air filters affecting airflow
✔ Loose wiring or corroded sensor connectors
✔ A tripped or damaged compressor temperature switch
✔ Frost formation due to incorrect coil temperature reading
⚙️ For Inverter Carrier Units
Inverter units may include additional sensors in the indoor and outdoor units, such as:
Compressor discharge temperature sensor
Condenser coil outlet sensor
Outdoor air temperature sensor
High-temperature safety switch
Typical sensor values:
10 kΩ at 25°C (77°F) → most indoor & outdoor sensors
55 kΩ at 25°C → compressor discharge sensor
A failure or abnormal reading in any of these components can cause the E4 error to appear immediately at startup or during operation.
🛠️ How to Diagnose and Fix the E4 Error (Step-by-Step)
Disconnect power for several minutes to reset the control board.
Clean the indoor air filter and verify proper airflow.
Inspect the fans, coils, and wiring harness for loose or damaged connections.
Measure each sensor with a digital multimeter:
0 Ω → short circuit
∞ Ω → open circuit
Normal kΩ reading → sensor functional
Warm the sensor with your hand to confirm resistance decreases (NTC behavior).
Test the compressor temperature switch for continuity.
If all sensors are normal, the issue may be in the electronic control board.
📌 This Video Is Perfect For
HVAC technicians
Air conditioning repair students
Homeowners troubleshooting Carrier AC issues
Anyone who wants to understand the E4 error code in depth