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Error code reference

Coleman Furnace Error Code 2 FLASH

Combustion air pressure switch closed; the normally open pressure switch contacts are stuck in the closed…

Coleman codesColeman furnace codes

Combustion air pressure switch closed; the normally open pressure switch contacts are stuck in the closed position, indicating a faulty pressure switch or mis-wiring.

First step from the service manual

Check pressure switch and wiring.

The complete diagnostic procedure includes additional test steps, resistance specifications, wiring diagram references, and component test points.

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What 2 FLASH means on a Coleman furnace

The 2 FLASH error code on a Coleman furnace indicates that the combustion air pressure switch is reading as closed at a time when it should be open. The pressure switch is a normally open (NO) safety device that closes only when the inducer motor creates sufficient negative pressure (draft) through the heat exchanger and flue system. When the control board detects that this switch is already closed before the ignition sequence begins, it locks out operation and flashes the fault code, because a switch that is stuck closed cannot provide meaningful proof of draft airflow.

The most common cause of this fault is a failed pressure switch with contacts that have welded or mechanically stuck in the closed position. However, mis-wiring is also a direct cause listed for this code. If a technician has recently serviced the unit or wiring has been disturbed, the pressure switch circuit may be incorrectly connected, creating a continuous closed signal to the control board. In either case, the board interprets the condition as an unsafe or inaccurate input and prevents the furnace from firing.

Diagnosis begins with inspecting the pressure switch wiring harness for pinched, crossed, or incorrectly routed wires. With the furnace powered down, a technician can use a multimeter set to continuity or resistance mode to check whether the pressure switch contacts are open as expected at rest. A normally open switch that shows continuity at rest confirms a faulty switch. If wiring checks out and the switch tests bad, the switch will need replacement to resolve the fault.

Source: manufacturer service documentation.

Common causes of 2 FLASH

  1. 01

    Faulty pressure switch with stuck contacts

    Part replacement

    The pressure switch contacts have failed in the closed position due to wear or an internal mechanical fault. Testing with a multimeter at rest will show continuity across a switch that should read open.

  2. 02

    Mis-wiring at the pressure switch

    Wiring / connection

    Incorrect wiring connections at the pressure switch terminals can create a false closed signal to the control board. This is especially common after recent service work or repairs on the unit.

  3. 03

    Damaged or shorted wiring harness

    Wiring / connection

    A pinched, chafed, or shorted wire in the pressure switch circuit can complete the circuit unintentionally, mimicking a closed switch. Inspect the harness routing for any contact with sharp sheet metal edges or heat sources.

  4. 04

    Moisture or contamination inside the switch

    Part replacement

    Condensation or debris inside the pressure switch housing can cause internal contacts to bridge and stick closed. This is more likely in older units or installations with drainage issues near the switch.

See the test procedure for each cause

Frequently asked questions about 2 FLASH

What does 2 FLASH mean on a Coleman furnace?
The 2 FLASH code means the combustion air pressure switch is detected in the closed position when it should be open. This is a normally open safety switch that should only close when the inducer motor generates adequate draft. If the control board sees it closed at the wrong time, it assumes the switch is faulty or the wiring is incorrect and shuts down operation to prevent an unsafe condition.
Can I fix a 2 FLASH error on my Coleman furnace myself?
A knowledgeable DIYer can inspect the pressure switch wiring for obvious mis-connections or damage without special tools. However, confirming whether the switch itself has failed requires a multimeter to test continuity across the switch terminals at rest. If the switch is confirmed bad, replacing it involves working inside the furnace cabinet and disconnecting gas-adjacent components, so many homeowners prefer to have a qualified technician handle the repair.
Is a 2 FLASH error on a Coleman furnace a safety hazard?
The furnace is designed to lock out when this code appears, which means it will not attempt to fire until the fault is resolved. This lockout is a built-in safety response. While the code itself indicates a control circuit fault rather than a gas or combustion emergency, you should not attempt to bypass the pressure switch or its wiring to force the furnace to operate.
Will resetting my Coleman furnace clear the 2 FLASH code?
A power reset may temporarily clear the fault code, but if the pressure switch contacts remain stuck closed or the wiring is still incorrect, the code will return immediately when the furnace runs its startup self-check. Clearing the code without correcting the underlying fault will not allow the furnace to operate normally and may delay proper diagnosis.
How much does it cost to fix a 2 FLASH error on a Coleman furnace?
If the fault is a mis-wiring issue, a technician visit to inspect and correct the connections typically costs somewhere in the range of $75 to $200 depending on your area and the time involved. If the pressure switch itself needs replacement, parts and labor combined generally fall in the range of $100 to $350. Costs vary based on local labor rates and the specific switch required for your model.

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