Proline freezer displays E5 and may not defrost; heater does not warm during defrost cycle.

Safety first: Unplug the freezer before testing the heater. Do not touch the heater when energized.

Steps to diagnose E5:

• 1. Access the evaporator and heater: Remove the inner rear panel to expose the evaporator coil. The defrost heater is usually a metal or glass-encased element attached beneath or around the coil.
• 2. Visual inspection: Look for burn marks, broken heater sections, or melted connectors.
• 3. Test heater continuity: Disconnect the heater leads and measure resistance with a multimeter. A typical heater will show a finite resistance (often 50–300 Ω). If it reads open (OL), the heater is faulty.
• 4. Check thermal fuse (if present): Some Proline models include a thermal fuse in series with the heater. Test it for continuity; replace if open.
• 5. Inspect wiring and connectors: Ensure all connectors are tight and wires are not burned or brittle. Repair or replace damaged wiring with high-temperature-rated cable.
• 6. Replace faulty heater: Install a compatible Proline defrost heater assembly, securing it in the original mounting points and reconnecting wiring as per original layout.

Note: If the heater and wiring test good, the main control PCB or defrost relay may be defective. This typically requires a technician to diagnose and replace the board.