Lennox Furnace Error Code 2 Flashes

The 2 Flashes code on a Lennox furnace with control board 103085 means the pressure switch is detected in a closed state before the combustion air inducer motor has been turned on. This is a safety fault because the pressure switch should only close after the inducer builds up airflow. The furnace locks out to prevent unsafe operation until the fault is resolved.

Yes, this fault code exists specifically to protect your home. The furnace shuts down because the pressure switch, which monitors safe airflow through the venting system, is signaling incorrectly. Running the furnace without resolving this fault could mask a real venting or airflow problem, so the issue should be diagnosed and corrected before relying on the system for heat.

Repair costs depend on the root cause. If only hose cleaning or repositioning is needed, costs may be limited to a service call fee, typically in the range of $75 to $150. A replacement pressure switch generally runs between $20 and $80 for the part, plus labor. If the control board 103085 is faulty, parts and labor combined can range from $300 to $600 or more depending on your region and service provider.

Start by inspecting the pressure switch hose for kinks, cracks, moisture, or blockages and clear or replace the hose if needed. Next, test the pressure switch itself for continuity with the inducer off. If the switch contacts are closed when they should be open, the switch needs to be replaced. If the hose and switch both check out, inspect the wiring between the switch and the control board for any shorts or damage.

Resetting the furnace by cycling the power may temporarily clear the fault and allow a restart attempt, but the error will return if the underlying problem is not fixed. If the pressure switch is stuck closed or the hose is obstructed, the fault will reappear almost immediately during the next startup sequence. A proper diagnosis and repair of the root cause is necessary for a lasting fix.