E3
MrCool Low-Pressure Protection / Refrigerant System Underpressure

Indoor unit shows E3 and system shuts down, often during hot weather or heavy load.

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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

Refrigerant leak in line set or coil, Clogged expansion device, Severely dirty indoor or outdoor coil reducing heat exchange, Compressor not pumping correctly

How to Fix / Troubleshooting

Safety first: Do not attempt to open the refrigerant circuit. Turn off power before any inspection.

User checks:

  • Filters and coils: Ensure indoor filters are clean and both indoor and outdoor coils are free of heavy dirt and debris.
  • Line set inspection: Visually inspect the insulated refrigerant line set between indoor and outdoor units for oil stains, physical damage, or kinks.
  • Check for ice: Look for ice buildup on the outdoor suction line or indoor coil (after removing front cover). Ice suggests low charge or airflow issues.

Technician required: E3 almost always indicates a refrigerant-side problem. A licensed HVAC technician must locate leaks, repair them, evacuate, and recharge the system to MrCool specifications. Continued operation may damage the compressor.

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Repair Difficulty

Professional Required 5/5

Required Part

Refrigerant Line Set
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