Furnace starts but shuts down shortly after ignition; E05 displayed, blower may continue to run.

Safety: Turn off power before removing panels. Components may be hot; allow cooling time.

• Replace or clean air filter: Locate the furnace filter (in return grille, filter rack, or blower compartment). If dirty or clogged, replace with the correct size and airflow rating recommended by Alpha.
• Check vents and registers: Ensure all supply registers and return grilles are open and not blocked by furniture, rugs, or debris.
• Inspect blower operation: With panels in place and power restored, set the thermostat fan to ON. Confirm the Alpha blower motor starts promptly and runs smoothly. If it hums, starts slowly, or does not run, the blower motor or capacitor may be failing.
• Reset furnace: Some Alpha models have a manual reset high limit. If accessible, press the reset button on the limit switch (if present). If the limit trips repeatedly after fixing airflow, the switch or heat exchanger should be evaluated by a technician.

Persistent E05 after airflow corrections indicates a deeper issue (blower, limit switch, or heat exchanger) that requires professional diagnosis.