Furnace shuts down randomly during operation without displaying an error code.

Safety first: Disconnect power before tightening connections or replacing components.

Steps:

• 1. Check power source: Ensure the plug fits tightly in the outlet and the cord is not being pulled or flexed excessively. Avoid using extension cords.
• 2. Inspect wiring harnesses: Open the control compartment and gently tug on each connector to ensure it is secure. Look for discolored or overheated terminals.
• 3. Examine safety switches: Wiggle wires at high limit, low limit, and vacuum switches while the unit is off. Replace any switch that shows signs of heat damage or intermittent continuity.
• 4. Control board cooling: Make sure the control board area is not blocked and that internal fans (if equipped) are working. Overheating can cause random resets.
• 5. Monitor operation: After tightening and inspecting, run the furnace and observe. If random shutdowns continue, a technician should perform more detailed electrical testing.