Heater will not start at all; display is blank and no lights are on.

Safety first: High voltage is present. Turn off the breaker before opening the electrical compartment.

• Check breaker and disconnect: Verify that the heater’s dedicated breaker is on and that any external disconnect switch is in the ON position.
• Inspect power wiring: Remove the electrical access cover and confirm that line wires are securely attached and not burnt.
• Test internal fuse: Locate and check the low-voltage fuse on the control board. Replace only with the same rating if blown.
• Transformer check (advanced): With power on and using proper precautions, measure the transformer’s secondary voltage. If there is no low-voltage output, the transformer may need replacement.
• Call a professional: If you are not comfortable working with electricity or the unit remains dead, contact a qualified technician.