Indoor unit displays E4 and the unit shuts down, often after running for some time in cooling mode.

Safety first: Turn off power at the breaker. Do not attempt to open the sealed refrigeration system yourself.

• Step 1 – Clean the outdoor condenser coil:
  • Remove leaves, plastic bags, and debris from around the outdoor unit.
  • Use a soft brush or low-pressure water to clean dirt from the coil fins (avoid bending fins).
• Step 2 – Check outdoor fan operation:
  • Restore power and briefly run the unit.
  • Confirm the outdoor fan starts promptly and runs at normal speed.
  • If the fan is slow, noisy, or not starting, turn power off and inspect the fan motor and capacitor (if fitted).
• Step 3 – Inspect discharge sensor:
  • With power off, locate the discharge line sensor clipped to the small copper pipe near the compressor.
  • Check that it is firmly attached and the wires are intact.
• Step 4 – When to call a technician:
  • If E4 persists after cleaning and verifying fan operation, a professional should check refrigerant charge, discharge sensor resistance, and compressor condition.
  • Do not attempt to add refrigerant or open service valves without proper certification.