ACiQ EC52

What does ACiQ EC52 mean?

EC52 indicates an outdoor unit coil (condenser) temperature sensor (T3) error. The system flags this open-circuit or short-circuit fault when the sensor's sampling voltage is lower than 0.06V or higher than 4.94V, which falls outside the valid window for a healthy T3 sensor and signals a wiring or sensor problem.

Symptoms

• EC52 shown on the display
• Outdoor unit stops or runs abnormally
• Incorrect coil temperature regulation or defrost behavior
• Fault isolated to the outdoor coil sensor circuit

Common causes

• Open or short circuit in the T3 coil temperature sensor
• Loose or damaged sensor wiring or connector
• Out-of-range sensor resistance value
• Faulty outdoor PCB sensor input

Diagnostic steps

1. 01

   Inspect the sensor wiring

   Check the connection between the T3 coil temperature sensor and the outdoor PCB and ensure it is properly wired.

2. 02

   Measure the sensor resistance

   Measure the sensor's resistance value and compare it to the appendix table; replace it if outside acceptable parameters.

3. 03

   Correct the connection

   Repair or reseat any loose or damaged wiring found at the sensor or board.

4. 04

   Replace the outdoor PCB if needed

   If the sensor and wiring are good, replace the outdoor PCB.

When to call a professional

Verifying an out-of-range coil sensor with a meter and replacing the sensor or outdoor board requires accessing the outdoor unit's electronics, which can hold a charge after power-off. If EC52 persists after a connection check, contact a licensed HVAC technician. Resistance testing against the manufacturer's table and outdoor board replacement should be performed only by a qualified service professional.