How to Fix / Troubleshooting

Safety first: Before opening the furnace, ensure the circuit is de‑energized at the breaker.

Check external power: Verify that the wall switch (if fitted) is on and the circuit breaker or fuse for the furnace has not tripped or blown.
Inspect power cord and plug: For plug‑in models, ensure the plug is fully inserted and the outlet is live.
Internal fuse: With power off, open the electrical compartment and check any fuses on the Sime control board. Replace only with identical rated fuses.
Check main switch: Test the furnace's own power switch for continuity. Replace if faulty.
If still dead: The control board may have failed and should be replaced by a technician.

Furnace will not start at all; no display or lights on the control panel.

Possible Causes