Daikin EWAD Fault Code U4
Daikin EWAD Fault Code U4 is a warning alarm indicating: Indoor/outdoor communication abnormality. The most common causes include Communication cable between indoor and outdoor units damaged. Estimated repair time: 1-3 hours (requires board replacement, configuration, and commissioning). This alarm requires immediate attention by a certified HVAC technician.
Alarm Description
Indoor/outdoor communication abnormality
Brand: Daikin | Model: EWAD (Screw Compressor Chiller) | Code: U4 | Severity: Warning
Observable Symptoms
- Controller display shows communication error or blank screen
- BAS/EMS system shows chiller as offline or in alarm state
What to Check First
Before diving into detailed diagnostics, start with this quick first check:
Probable Causes
- Communication cable between indoor and outdoor units damaged
- Communication board failure
- Electrical interference on communication line
Recommended Inspection Steps
- Check communication cable continuity and connections
- Inspect for cable damage or moisture
- Verify communication board LED status
- Replace communication board if faulty
- Check for sources of electrical interference
Required Tools & Equipment
- Digital multimeter
- Safety PPE (gloves, safety glasses, face shield)
- Wire tracing and continuity tester
Estimated Repair Time
1-3 hours (requires board replacement, configuration, and commissioning)
When to Call a Professional
- If the fault persists after completing all recommended inspection steps
- If you observe unusual noises, vibrations, or oil leaks from the compressor
- If refrigerant charge levels are outside OEM specifications and EPA-certified recovery is needed
- If electrical measurements show voltage imbalance greater than 2% between phases
- If the fault recurs immediately after reset, indicating an unresolved safety condition
- Contact an authorized Daikin service representative for warranty-covered repairs
Related Fault Codes
Other Daikin EWAD codes that may be related:
OEM Service Manual Reference
OEM Reference: Daikin EWAD Air-Cooled Screw Chiller Service Manual. Available through Daikin Applied technical support.
Frequently Asked Questions
What does Daikin EWAD fault code U4 mean?
Fault code U4 on a Daikin EWAD chiller indicates: Indoor/outdoor communication abnormality. This is a warning alarm that requires diagnostic attention.
What causes Daikin EWAD alarm code U4?
Common causes include: Communication cable between indoor and outdoor units damaged; Communication board failure; Electrical interference on communication line
How do I fix Daikin EWAD error code U4?
Follow the recommended inspection steps below. Start with the quick check, then proceed through each step. If the fault persists after all steps, contact an authorized Daikin service representative.