ACiQ EC54

What does ACiQ EC54 mean?

EC54 indicates a compressor discharge temperature sensor (TP) error. The TP sensor measures the temperature of refrigerant leaving the compressor, which the control uses for protection. The fault is flagged as an open or short circuit when the sensor's sampling voltage is lower than 0.06V or higher than 4.94V, outside the valid range.

Symptoms

• EC54 shown on the display
• Outdoor unit stops or runs abnormally
• Loss of compressor discharge-temperature protection input
• Fault isolated to the TP sensor circuit

Common causes

• Open or short circuit in the TP discharge 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 TP discharge 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

The discharge sensor sits at the compressor in the outdoor unit's electrical and refrigerant area, and confirming the fault means resistance testing and possible board replacement around capacitor-charged electronics. If EC54 persists after a connection check, contact a licensed HVAC technician. This protection-sensor diagnosis and any board replacement should be handled only by a qualified service professional.