Freezer shows E4, may stop cooling or run erratically.

Safety first: Unplug the freezer. Ice and water around electrical parts are hazardous—keep the work area dry.

• Check for heavy frost: Remove baskets and inner rear panel to inspect the evaporator. A solid block of ice indicates defrost failure.
• Test defrost heater: Locate the heater at the base or around the evaporator coil. Disconnect its wires and measure resistance. A typical heater will show a few tens of ohms. Infinite resistance means it is open and must be replaced.
• Inspect defrost thermostat/fuse: Many Haier freezers use a defrost thermostat or thermal fuse clipped to the evaporator tubing. Test continuity at freezing temperature (or after cooling with ice). No continuity when cold indicates a failed safety device.
• Check wiring and connectors: Look for burnt connectors or melted insulation near the heater. Repair or replace damaged wiring with high-temperature-rated wire.
• Control board evaluation: If heater and thermostat test good, the defrost relay or triac on the main control PCB may be defective. Inspect for burnt spots. If suspected, replace the control board as a unit.
• Manual defrost: Before reassembly, fully defrost the evaporator using a hair dryer on low or by leaving the unit unplugged with doors open (protect the floor from water). Do not chip ice with sharp tools.