Boiler shows E13; may indicate external thermostat or control input fault.

Safety first: Turn off power before working on control wiring.

• Check external controls: Verify that the room thermostat and any external programmer are powered and set to call for heat.
• Inspect wiring at boiler terminals: Open the boiler's wiring compartment and check that the external control terminals (e.g., TA, COM, NO) are correctly wired according to the Elnur manual.
• Test with a link (temporary): For testing only, fit a link wire between the boiler's control terminals that should be closed on demand. Restore power and see if E13 clears and the boiler starts. Remove the link after testing.
• Trace cable faults: If the boiler works with the link but not with the external controls, inspect the cable run for damage, junction boxes, or loose connections.
• Replace faulty thermostat/programmer: If wiring is sound, the external control device may be defective and should be replaced.

Warning: Only use a link for diagnostic purposes; ensure correct control devices are fitted for normal operation.