Display shows E4 and the unit may not defrost properly, leading to ice buildup on the evaporator.

Safety first: Disconnect power before working near the evaporator or heater. Risk of electric shock and sharp edges.

Steps to diagnose E4 defrost issues:

• 1. Manually defrost: Turn off the cooler and leave the door open until all ice on the evaporator melts. Place towels to absorb water. Do not use heat guns or open flames.
• 2. Access evaporator and defrost components: Remove interior shelves and the rear inner panel. Identify the evaporator coil, defrost heater (usually a tube or wire element at the base of the coil), and defrost sensor clipped to the coil.
• 3. Check defrost sensor: Disconnect the defrost NTC and measure resistance at around 0–5°C (place the sensor in ice water). Compare to Brandt's NTC chart. Replace if readings are out of range or intermittent.
• 4. Test defrost heater: With the unit unplugged, measure resistance across the heater terminals. A typical heater will show a few tens of ohms. Infinite resistance indicates an open heater that must be replaced.
• 5. Inspect wiring and connectors: Look for burnt connectors, brittle insulation, or loose plugs between the heater, sensor, and main PCB. Repair or replace as needed.
• 6. Control board check: If both heater and sensor test good, the defrost relay or triac on the main control board may be faulty. This usually requires PCB replacement.
• 7. Reassemble and test: Refit the evaporator cover and shelves, restore power, and monitor operation over 24 hours. The E4 code should not reappear if the defrost system is functioning correctly.