Indoor unit does not start at all; no blower, no display, thermostat blank

Safety first: Use caution around electrical panels. Turn OFF main power if necessary.

• Step 1 – Check breaker: Verify the air handler/furnace breaker is ON. Reset once if tripped.
• Step 2 – Door switch: Ensure the blower door is properly closed and engaging the safety switch.
• Step 3 – Internal fuses: Some Day & Night air handlers have internal line fuses. Inspect and replace only with identical type and rating.
• Step 4 – Terminal block: Check that incoming power wires are tight at the indoor unit terminal block.