Rollout switch open

What is going on

The rollout switch has opened and the furnace will not run. A rollout switch trips when flame or hot gas spills out of the burner compartment, so treat it as a real warning and never as a nuisance trip. Switch the power off before you open the furnace, and do not bypass the switch to get heat.

Likely causes

• Gas pressure too high, which pushes the flame out of the burner area
• Burners misaligned
• Restricted heat exchanger or venting, causing combustion gases to spill out

Check in this order

1. Turn power off before service.
2. Look for scorching, soot or melted wire insulation around the burner compartment.
3. Check and correct gas pressure. This is licensed gas technician work.
4. Check and correct burner alignment.
5. Check and correct restrictions in the heat exchanger or venting.
6. Only after the cause is fixed, reset or replace the switch, then watch a full cycle. Check for carbon monoxide at the vent and in the room.

More furnace guides

• Airflow lower than demanded, furnace runs on low stage when high stage is expected
• Alternate combustion air opening (upflow or horizontal)
• Alternate vent/flue location (upflow or horizontal left)
• Annual inspection checklist
• Auxiliary limit control (location and purpose)
• Auxiliary limit switch open (blower compartment)