How to Change the Rollout Limit on a Furnace

Residential gas furnaces contain safety components known as rollout limit switches. These switches are designed to close the internal gas valve and disable the ignition system if they detect combustion outside of the dedicated combustion area. After a rollout limit lockout, press the reset button at the center of the component. If you still can't start the furnace after the reset, it's time to replace the rollout limit switch. The need for frequent rollout limit resets and replacements may indicate an obstructed furnace flue.

Screwdriver
Needle-nose pliers

Instructions

- 1
  Shut off the electricity to the furnace from your circuit breaker box; move the corresponding switch into the "Off" position. Rotate the gas valve that feeds the furnace all the way to the left to disrupt the gas supply while changing the rollout limit.
- 2
  Remove the screws securing the burner access panel to the front of the furnace; the type and number of screws varies by model. Slide the panel up and pull it toward you if your model uses retaining tabs instead of screws.
- 3
  Find the rollout limit switch mounted just above the gas burners. Pull the small metal wiring connectors with needle-nose pliers to detach them from the limit switch terminals. Remove the screws securing the component to the burner cabinet. Discard the faulty rollout limit switch, but reserve the screws.
- 4
  Hold the new rollout limit switch to the burner cabinet. Align the screw holes on the cabinet with the ones on the component. Insert and tighten the reserved screws. Slide the metal wiring connectors onto the rollout switch terminals, using the needle-nose pliers.

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