No lights on Miller furnace control board; furnace completely dead.

Safety: You will be working near line voltage. Turn off the breaker before opening electrical compartments.

• Check breaker and switch: Verify the furnace circuit breaker is ON and the furnace service switch (often on or near the unit) is in the ON position.
• Inspect door switch: Ensure the blower door is fully closed and engaging the door switch.
• Check internal fuse: With power off, locate and test the low-voltage fuse on the control board. Replace if blown, but investigate for shorts in thermostat or accessory wiring.
• Test transformer: With power on and using a multimeter, verify 120V at the primary of the transformer and approximately 24V at the secondary. If primary has power but secondary is dead, replace the 24V control transformer.