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

Safety first: Be cautious around electrical panels. If unsure, contact an electrician.

Steps:

• Check the home electrical panel for a tripped breaker feeding the furnace. Reset once if tripped.
• Verify that the furnace service switch (often looks like a light switch near the unit) is in the ON position.
• Remove the blower door and inspect the internal line-voltage fuse (if equipped) and wiring connections in the furnace junction box.
• If there is still no power indication on the CTC control board, the transformer or internal wiring may be faulty and should be checked by a technician.