Error Code: EC 53 – Outdoor Ambient Temperature Sensor (T4) Error

Error Code: EC 53 – Outdoor Ambient Temperature Sensor (T4) Error

What this means:
The T4 sensor, which monitors outdoor ambient temperature, is showing a fault due to an open or short circuit, or an abnormal signal voltage. If the sampling voltage is below 0.06V or above 4.94V, the system will shut down and trigger EC 53TS23.

Try this first (quick reset):

1. Turn off the power to the unit.

2. Wait 2 full minutes.

3. Turn the unit back on and check if the error clears.

• If the error clears — the issue was likely temporary.

• If the error remains — proceed with diagnostics.

Next steps (for technicians):

1. Inspect the T4 sensor wiring:

   • Ensure the connection between the sensor and outdoor PCB is secure and not corroded or damaged.

2. Measure the sensor resistance:

   • If the resistance is out of range → replace the T4 sensor.

   • If within range but the issue persists → replace the outdoor PCB.

What you might need:

• T4 ambient temperature sensor

• Outdoor PCB

• Connection wires

Helpful tip:
T4 is often part of a shared temperature sensor harness with T3 and TP. Double-check sensor group wiring if other EC 5x codes are also present.

Click here to view the detailed guide.TS23