Seeing an E0 error on your Della mini split display? This code means your indoor unit (IDU) and outdoor unit (ODU) aren't communicating properly.

When abnormal communication lasts longer than 120 seconds, the system shuts down to protect itself.

This guide follows Della's standard troubleshooting flow. It walks you through each check in the correct order. Don't skip steps, as doing so may lead to unnecessary part replacement.

What Does E0 Mean?

E0 indicates a communication failure between the indoor and outdoor units. Both units rely on constant signal exchange to work together. When that link breaks, the system stops operation.

Common causes include:

• Wires connected to wrong terminals
• Loose or damaged communication wiring
• Poor grounding connections
• Extended wires with weak insulation
• Electrical interference from nearby high-power equipment(such as transformer cabinets, generators, etc)
• Failed control board in either unit

Now let's work through the troubleshooting steps in order.

Step 1: Check IDU–ODU Wiring Connections

Start with the most common cause. Compare the wiring between your indoor and outdoor units with the official wiring diagram. Look for:

• Wires connected to the wrong terminals
• Loose terminal screws
• Wires that can be pulled out easily

If wiring is incorrect or loose:

• Turn off power to the system
• Reconnect and tighten all terminals
• Restore power

Then check the display:

• If E0 disappears → Stop here. Problem solved.
• If E0 remains → Continue to Step 2

Step 2: Inspect Communication Wire and Grounding

Next, check the condition of the communication and earth (ground) wiring.

Focus on:

• Communication wire insulation damage or aging
• Poor or loose grounding connections
• Extended or spliced wires with weak insulation
• Loose terminal connections

If you extended the original communication wires during installation, pay extra attention to those splice points. Poor connections in extended wiring cause many E0 errors.

If wiring or grounding is not in good condition:

• Replace or reconnect the affected wires
• Restore power

Then observe the unit:

• If E0 disappears → Stop here
• If E0 remains → Continue to Step 3

Step 3: Confirm Outdoor Unit Power Supply

Before testing communication voltage, confirm that the outdoor unit has normal power supply.

Check:

• Circuit breaker and disconnect switch
• Outdoor power wiring connections

If the outdoor unit does not have power:

• Restore proper power supply first

Communication troubleshooting should stop at this point. Once outdoor power is confirmed normal, proceed to the next step.

Step 4: Measure Voltage from the Indoor Unit Terminal

Now check whether the indoor unit is supplying correct voltage to the outdoor unit.

At the indoor unit terminal, measure voltage between:

• L and N, or
• Terminal 2 and 3, depending on the model

Expected voltage:

• 230V or 115V, according to unit specifications

You'll need a multimeter for this step.

If NO voltage is detected:

• Check the power supply connection
• Replace or reconnect wiring if needed

If voltage cannot be restored, the outdoor PCB may not be receiving power correctly. The outdoor PCB should be replaced.

After replacement, restore power and check:

• If E0 disappears → Stop here
• If E0 remains → Continue troubleshooting

If voltage is normal:

Proceed to the next step.

Step 5: Check ODU PCB LED5 Status

Open the outdoor unit control box and locate the PCB indicator labeled LED5. The PCB is the control board that manages your unit's operations.

If LED5 is OFF:

• The outdoor PCB is not operating normally
• Replace the ODU PCB

Restore power and check:

• If E0 disappears → Stop here

If LED5 is ON:

Proceed to Step 6.

Step 6: Check Whether LED5 Is Flashing

Observe the LED5 behavior carefully.

According to the troubleshooting flow, first replace the IDU PCB. The indoor PCB is replaced first because it initiates communication with the outdoor unit.

After replacing the indoor PCB:

• Restore power
• Check the display

Result check:

• If E0 disappears → Stop here
• If E0 remains → Replace the ODU PCB

After replacing the outdoor PCB, the troubleshooting process ends.

Quick Reference Checklist

Here's a summary of the troubleshooting steps:

• Check and correct all wiring between indoor and outdoor units
• Inspect communication and ground wire condition
• Confirm outdoor unit has normal power supply
• Measure voltage at the indoor unit terminal
• Check the LED5 indicator on the outdoor control board
• Replace the IDU PCB first if LED5 is ON
• Replace the ODU PCB if the problem continues

Key Notes

Always restore power and check whether E0 disappears after each corrective action. This helps you identify exactly which fix solved the problem.

Replace the IDU PCB before the ODU PCB when LED5 is ON. This follows the specified flow because the indoor unit initiates communication.

Do not skip steps. Following the order prevents unnecessary part replacement and saves you time and money.

When to Call a Professional

If you're not comfortable working with electrical components or control boards, contact a qualified HVAC technician. Working with high-voltage components requires proper training and safety equipment.

A technician can also help when:

• The error returns after you've tried basic fixes
• You need to replace a control board
• You can't identify the source of the problem

Read More: Understanding Mini Split Error Codes: A Quick Guide for Della Models