H4
Danby Indoor-Outdoor Communication Fault (Split Systems) or General Protection

Display shows H4, unit may not cool or may shut down intermittently.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Damaged communication cable between indoor and outdoor units, Loose terminal connections, Incorrect wiring polarity, Faulty indoor or outdoor PCB

How to Fix / Troubleshooting

Applies mainly to Danby split air conditioners.

Safety: Turn off the breaker to the system before opening any electrical covers.

Steps:

  • 1. Check wiring between units: Remove the electrical covers on both indoor and outdoor units. Verify that the communication terminals (often labeled 1-2-3 or L-N-S) are wired identically at both ends and that screws are tight.
  • 2. Inspect cable: Look for signs of rodent damage, UV cracking, or mechanical damage along the interconnecting cable. Replace if compromised.
  • 3. Polarity and grounding: Ensure line and neutral are correctly connected and that the ground is secure.
  • 4. Board inspection: Inspect both indoor and outdoor PCBs for burn marks or swollen components. Replace the defective board as indicated by visual inspection or manufacturer diagnostics.
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Repair Difficulty

Professional Required 5/5

Required Part

Outdoor Control Board
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