Heater shows E13 and stops; may be accompanied by unusual compressor noise

Danger: High voltage and high current are present. Only perform basic visual checks unless you are qualified. Do not bypass safety devices.

• Check supply voltage: Verify that the heater is supplied with the correct voltage (single-phase or three-phase as specified) and that breakers are not tripping.
• Inspect power connections: With power off, tighten all main power terminal screws and check for signs of overheating (discolored insulation, burnt smell).
• Listen for compressor start attempts: When power is restored and a heat demand is present, listen for the compressor trying to start and then tripping. Repeated hard starts indicate a compressor or start component issue.
• Do not repeatedly reset: Avoid repeatedly resetting the unit if E13 returns immediately; this can damage the compressor further.

Compressor overcurrent faults require professional diagnosis with proper test equipment. Contact a qualified refrigeration technician to test compressor windings, contactor, and current draw.