Display shows E4 and the wine cooler may not defrost properly, leading to ice buildup and poor cooling.

Safety: Unplug the wine cooler before testing any heater or high-voltage components. The defrost heater operates at mains voltage.

Steps to address E4:

• Defrost manually first: With the unit unplugged, open the door and allow all ice on the evaporator to melt. Place towels to catch water.
• Access the evaporator and heater: Remove interior shelves and the rear interior panel. Locate the defrost heater, typically a metal or glass-encased element mounted at the base or around the evaporator coil.
• Visual inspection: Look for breaks, burn marks, or discoloration on the heater and its wiring. Check for a small thermal fuse or thermostat in series with the heater.
• Test heater continuity: Disconnect heater leads and measure resistance with a multimeter. A typical heater will show finite resistance (often 50–300 Ω). Infinite resistance indicates an open heater that must be replaced.
• Check thermal fuse/thermostat: If present, test for continuity at room temperature. An open safety device will prevent the heater from energizing.
• Inspect wiring to control board: At the rear, verify that the heater wiring harness is intact and firmly connected to the main control PCB.
• Replace faulty parts: Install a Haier-compatible defrost heater and/or thermal fuse/thermostat as needed. Secure wiring away from sharp edges and hot surfaces.
• Reassemble and test: Reinstall panels, restore power, and monitor for proper defrost cycles and absence of E4.

Note: If the heater circuit tests good but E4 persists, the defrost relay or control logic on the main control PCB may be defective and should be serviced by a technician.