How to Bypass a Pressure Switch on a Lennox G16 Gas Furnace

James Clark

The pressure switch on a Lennox G16 gas furnace monitors whether the air blower is in operation. The switch activates with air force pushing a plunger in the mechanism, which closes the circuit.

If your Lennox does not activate normally during the ignition sequence, try running a quick bypass of the pressure switch to determine if it is the problem. Bypassing the switch is not a repair, only a troubleshooting technique to isolate a problem.

  1. Shut off the Lennox at the thermostat and switch off the circuit breaker that controls power to the furnace. Wait for the G16 to cool.

  2. Take out the nuts holding the service cover to the side of the Lennox using the nut driver. Looking inside the unit, locate the round pressure switch connected to a flexible plastic hose and two wires. The switch is held in position by an L-shaped metal bracket.

  3. Unclip the two wires from the metal contacts on the side of the pressure switch. Each wire pulls off with a U-shaped connector on the end.

  4. Splice the connectors on the two wires together with a short piece of electrical tape cut from the roll with scissors. Do not wrap the wires tightly.

  5. Switch on the circuit breaker and activate the Lennox at the thermostat. If the furnace switches on and begins operating normally, the pressure switch is defective and must be replaced for safe operation of your furnace.