Display shows Er13 and furnace shuts down; may be accompanied by unusual fan behavior.

Safety first: Turn off and unplug the furnace. Allow it to cool before accessing the combustion blower or venting.

Steps:

• 1. Inspect air intake: Check the outside air intake (if installed) for blockages such as snow, leaves, or debris. Clear any obstructions.
• 2. Check venting: Ensure the exhaust vent is clear and properly installed. Clean ash and soot from the vent and exhaust housing.
• 3. Access the combustion blower: Remove the rear or side panel to reach the combustion blower mounted on the exhaust housing.
• 4. Inspect blower wheel and housing: Look for heavy ash buildup or foreign objects in the blower wheel. Clean thoroughly.
• 5. Test blower operation: With power restored and under supervision, start the furnace and observe the combustion blower. If it fails to start, runs erratically, or is very noisy, the motor may be failing and should be replaced.
• 6. Check blower wiring and sensor (if equipped): Some models use a speed sensor or tachometer. Ensure its connector is secure and wiring is intact. Replace the sensor or blower assembly if defective.
• 7. Control board diagnosis: If the blower is good but not receiving proper power or feedback, the control board may be at fault. Have a technician test and replace the board if needed.