Error Code: EL 01 – Indoor & Outdoor Unit Communication Error

Error Code: EL 01 – Indoor & Outdoor Unit Communication Error

What this means:
The indoor unit is unable to communicate with the outdoor unit. This may be caused by a wiring issue, power supply fault, a failed control board, or a shorted component between the two units.

Try this first (quick reset):

1. Turn off power to the system completely.

2. Wait 2 full minutes.

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

• If the error disappears — the issue may have been temporary.

• If the error returns — continue below.

Next steps (for technicians):

• Measure the DC voltage between terminals N/L2 and S:

  • If value is fixed near 0 → check for wiring issues.

  • If alternating between -25V and +25V → signal is normal.

  • If always positive → likely fault in one of the PCBs.

• Check wiring between:

  • Indoor terminal and indoor PCB

  • Outdoor terminal and outdoor PCB

  • Between PCBs (if unit has more than one)

• Verify power LED status and whether W and 1 (L) are properly connected.

• Inspect and test high-voltage components (heater, fan, 4-way valve):

  • Unplug one by one and test resistance.

  • Replace any shorted components.

• Check expansion valve coil or replace if faulty.

• Test voltages from the IPM to the main PCB (5V and 12V lines):

  • If voltage is abnormal, replace the IPM board.

  • If communication still fails, replace the indoor or outdoor PCB, depending on test results.

What you might need:

• Indoor PCB

• Outdoor PCB

• IPM board

• Short-circuited component (if detected)

• Electronic expansion valve coil

• Communication wiring

Helpful tip:
Voltage between the communication terminals should alternate between -25V and +25V in a healthy system. A fixed voltage or always-positive reading helps identify which board is at fault.

Click here to view the detailed guide.TS02-S-INV