Unit displays E15; compressor does not start and outdoor unit remains off.

Safety first: Turn off power at the breaker before opening any covers. Verify no voltage is present at terminals before touching.

• Step 1 – Verify wiring order: At both indoor and outdoor terminal blocks, confirm that each terminal (often labeled 1–2–3 or L–N–S) has the same color wire at both ends. Correct any mismatches.
• Step 2 – Tighten terminals: Check all screws for tightness. Loose connections can cause intermittent communication.
• Step 3 – Inspect cable condition: Look for signs of rodent damage, UV cracking, or water ingress along the cable route. Replace damaged cable with the correct type and gauge.
• Step 4 – Power reset: After corrections, power off for 5 minutes, then restore and test.
• Technician tasks: If E15 persists, a technician should measure communication signals and may need to replace the indoor or outdoor PCB.