Lennox HVAC Unit ML193UH090XE48C

Turn off gas and electrical power to the furnace

Remove heating compartment access panel

Disconnect the gas supply line from the gas valve

Disconnect and label wires from gas valve

Disconnect ignitor wiring at 2 circuit plug

Disconnect and label wires from rollout switch

Disconnect and label flame sensor wire

Turn off electrical and gas supplies to the furnace

Mark all gas valve wires and disconnect them from valve

Remove gas supply line connected to gas valve

Remove sensor wire from flame sensor and disconnect 2-pin plug from the ignitor

Disconnect wires from flame roll-out switches

Remove four burner assembly screws at the vestibule panel and remove gas valve/manifold and burner box as a single unit

Read and understand all safety warnings before proceeding.

Disconnect all electrical power to the furnace before servicing.

Label all wires prior to disconnecting them.

Ensure all wires are reconnected correctly after servicing.

Verify proper operation after servicing.

Ensure the unit is properly grounded in accordance with national and local codes.

Use copper wire only. Do not use aluminum wire.

Prepare a shallow pan to empty condensate water

Remove the clean out cap from the condensate trap

Empty water from the condensate trap into the pan

Inspect the condensate trap for any damage or blockages

Reinstall the clean out cap on the condensate trap

Check that all tools and materials are removed from the work area

Turn the power back on to the furnace

WARNING! ELECTRICAL SHOCK, FIRE, OR EXPLOSION HAZARD.

Disconnect all electrical power to furnace before servicing.

Label all wires prior to disconnecting when servicing controls.

Ensure wires are reconnected correctly after servicing.

Filter Inspection and Maintenance

Inspect all air filters installed external to the unit.

Is cleaning or replacement of filters necessary?

If necessary, clean or replace the filters to ensure proper furnace operation.