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Error code reference

Coleman Furnace Error Code 1 FLASH

Ignition failure.

Coleman codesColeman furnace codes

Ignition failure.

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What 1 FLASH means on a Coleman furnace

The 1 FLASH error code on a Coleman furnace indicates an ignition failure, meaning the furnace attempted to light the burner but was unable to establish a flame within the allotted trial-for-ignition period. The ignition sequence typically involves the inducer motor energizing, a pressure switch confirming draft, the igniter heating to the required temperature, and gas valve opening to allow fuel flow. If the control board does not detect a flame signal from the flame sensor within the trial period, it will lock out and display this fault code.

Ignition failures can originate from several points in the sequence. A failed or weakened hot surface igniter is one of the most frequent culprits, as igniters degrade over time and may no longer reach the temperature needed to reliably light the gas. A faulty gas valve that does not open properly, low gas supply pressure, or a closed manual shutoff valve can also prevent combustion from occurring even when the igniter is functioning correctly.

The flame sensor is another common factor in ignition faults. If the sensor rod is coated with oxidation or residue, it may not conduct the microamp current needed to confirm a flame to the control board, causing the board to shut down the gas valve and log the fault. Additionally, problems with the inducer motor or pressure switch can prevent the ignition sequence from even reaching the igniter stage, resulting in the same lockout condition.

Source: manufacturer service documentation.

Common causes of 1 FLASH

  1. 01

    Weak or failed hot surface igniter

    Part replacement

    Over time, the igniter element degrades and may no longer reach sufficient temperature to light the gas. Inspect the igniter for visible cracks and measure its resistance to determine if it is within the acceptable range.

  2. 02

    Dirty or failed flame sensor

    Wiring / connection

    A flame sensor rod coated with oxidation or buildup cannot pass the small microamp current required to signal the control board that a flame is present. Cleaning the rod with fine steel wool or emery cloth often resolves this issue.

  3. 03

    Gas supply problem

    Wiring / connection

    The furnace cannot ignite if the gas supply pressure is too low or if a manual shutoff valve is closed. Verify the shutoff valve near the furnace is fully open and that other gas appliances in the home are operating normally.

  4. 04

    Faulty gas valve

    Part replacement

    If the gas valve does not open during the ignition sequence, no fuel reaches the burner even when the igniter is glowing. A failed valve typically requires replacement and should be tested by a qualified technician.

  5. 05

    Inducer motor or pressure switch issue

    Part replacement

    The ignition sequence will not advance to the igniter stage if the pressure switch does not confirm that the inducer motor has established proper draft. A blocked flue, a failed inducer motor, or a faulty pressure switch can all prevent the sequence from proceeding.

See the test procedure for each cause

Frequently asked questions about 1 FLASH

What does 1 FLASH mean on a Coleman furnace?
A 1 FLASH error code on a Coleman furnace indicates an ignition failure. The furnace attempted to light the burner during its normal ignition sequence but could not establish a flame within the allowed time period. The control board then shut the system down and is displaying this fault to indicate where the problem occurred. Common causes include a degraded igniter, a dirty flame sensor, or a gas supply issue.
Can I fix a 1 FLASH ignition failure on my Coleman furnace myself?
Some causes of a 1 FLASH code are within reach of a knowledgeable DIYer. Cleaning a dirty flame sensor, verifying that the gas shutoff valve is open, and visually inspecting the igniter for cracks are reasonable first steps. However, testing and replacing components like the gas valve, igniter, or control board involves working around gas lines and high-voltage components, which is best left to a qualified HVAC technician.
Is a 1 FLASH error on a Coleman furnace a safety hazard?
The 1 FLASH lockout is itself a safety response. The furnace shuts down rather than continuing to release unlit gas into the heat exchanger, which could create a dangerous condition. The lockout protects the home until the underlying fault is corrected. If you smell gas at any point, leave the home and contact your gas utility before attempting any inspection.
Will resetting the furnace clear the 1 FLASH error code?
Resetting the furnace by cycling the power or pressing the reset button may temporarily clear the lockout and allow the furnace to attempt ignition again. However, if the underlying cause is not corrected, the furnace will fail to ignite again and the 1 FLASH code will return. Repeated failed ignition attempts without addressing the root cause can sometimes introduce additional wear on components.
How much does it cost to repair a 1 FLASH ignition failure on a Coleman furnace?
Repair costs vary depending on the failed component. Cleaning a flame sensor is low cost and may only involve a service call fee, typically in the range of $75 to $150. Replacing a hot surface igniter generally costs between $100 and $250 including parts and labor. A gas valve replacement is more involved and can range from $200 to $600 or more depending on the model and local labor rates.

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