Safety: Turn off power at the breaker before opening the control compartment. Use a non-contact tester to confirm power is off.

Check thermostat wiring at furnace: Remove the blower door to access the control board. Verify R, W, Y, G, and C wires are firmly attached and not shorted together.
Inspect cable for damage: Follow the thermostat cable from the furnace entry point. Look for staples through the cable or rodent damage. Repair or replace as needed.
Verify transformer output: With power on and doors in place (door switch closed), measure between R and C on the board. You should see about 24 VAC. If low or zero, suspect the transformer or primary power.
Check line voltage polarity: Confirm hot and neutral are correctly wired at the furnace junction box. Incorrect polarity can cause nuisance lockouts on some Amana boards.

If you are not comfortable working with electrical wiring, contact a licensed technician.

Furnace does not respond to thermostat; LED flashes 8 times repeatedly.

Possible Causes