Does your furnace start its heating sequence but the burners won't ignite? A failed furnace gas valve is one possible cause.

SDG Duct Cleaning provides furnace repair in Cornwall, Ontario and throughout the surrounding SDG area. We're HVAC technicians—not just duct cleaners—and diagnosing gas valve and furnace ignition problems is part of troubleshooting a gas furnace that isn't producing heat.

The furnace gas valve controls the flow of gas to the burners. When the furnace reaches the proper point in its heating sequence, the control board sends a signal to the gas valve. The valve opens, gas flows to the burners, and the ignition system lights the gas.

If the gas valve doesn't open when it should, the furnace may appear to start normally but never actually produce heat.

What Does a Furnace Gas Valve Do?

Your furnace doesn't allow gas to flow simply because the thermostat calls for heat.

Several things normally happen first.

The inducer motor starts, the furnace proves the required draft conditions, and the hot surface igniter heats up. Once the necessary safety conditions have been satisfied, the furnace control board can energize the gas valve.

The valve then opens and supplies gas to the burners.

If the gas valve fails to open, the burners cannot ignite.

What Are the Signs of a Bad Furnace Gas Valve?

Some symptoms that may lead us to investigate the gas valve include:

• Furnace won't produce heat
• Furnace starts but burners don't ignite
• Inducer motor runs normally
• Hot surface igniter glows but burners don't light
• Furnace repeatedly attempts ignition
• Furnace eventually goes into ignition lockout
• Gas valve receives the proper electrical signal but doesn't open
• Furnace works intermittently
• Furnace displays an ignition-related fault code
• You hear the furnace starting but never hear the burners ignite

These symptoms don't automatically mean the gas valve is bad.

Proper diagnosis is especially important when dealing with the gas system of a furnace.

My Furnace Igniter Glows but the Burners Don't Light

This is one symptom that can lead us toward investigating the gas valve.

You may hear the inducer motor start and then see the hot surface igniter glowing, but the burners never light.

At this point, we need to determine what happens next in the furnace's sequence.

Is the furnace control board sending the proper signal to the gas valve?

Is the gas valve receiving that signal?

Is there an adequate gas supply to the furnace?

Is another control interrupting the sequence?

If the gas valve is receiving the proper signal but fails to open, the valve itself becomes a much stronger suspect.

Does No Flame Mean I Have a Bad Gas Valve?

No.

A furnace with no flame can have many possible causes.

The problem could involve the:

• Hot surface igniter
• Pressure switch
• Inducer or venting system
• Furnace control board
• Gas supply
• Wiring
• Gas valve
• Other furnace safety or ignition controls

This is why we don't recommend replacing a gas valve simply because the burners aren't lighting.

We need to determine how far the furnace gets through its normal heating sequence and where that sequence stops.

Can a Furnace Gas Valve Work Intermittently?

Yes, electrical and mechanical components can sometimes develop intermittent problems.

A furnace may operate normally during one heating cycle and then fail to ignite during another.

Intermittent furnace problems can be more difficult to diagnose because the equipment may be operating normally when the technician first arrives.

If you've noticed a pattern, tell us.

For example:

“Sometimes the igniter glows and the furnace lights, but other times it doesn't.”

Information like that can be useful when troubleshooting the system.

What If I Smell Gas Around My Furnace?

This is different from simply having a furnace that won't ignite.

If you smell a strong or persistent natural-gas odour, don't continue trying to operate or troubleshoot the furnace. Leave the area and contact your gas utility or emergency services from a safe location.

A suspected gas leak should be treated as a gas-safety issue, not simply as a normal furnace-repair call.

Should I Replace a Furnace Gas Valve Myself?

A furnace gas valve isn't a component we recommend homeowners replace themselves.

Replacing a gas valve involves working directly with the furnace's fuel-gas system, and the replacement valve must be appropriate for the furnace and properly installed, tested and set up.

If the gas valve is suspected of failing, the furnace should first be properly diagnosed.

Furnace Gas Valve Diagnosis in Cornwall, Ontario

You don't need to know whether your gas valve has failed before contacting us.

You may simply notice:

“My furnace starts but the burners don't light.”

“The igniter glows but there's still no heat.”

“My furnace keeps trying to ignite.”

“The furnace works sometimes but doesn't light every time.”

“My furnace is showing an ignition error.”

Those symptoms give us somewhere to begin.

SDG Duct Cleaning provides furnace troubleshooting and repair in Cornwall and surrounding SDG communities during our regular service hours. We'll diagnose the heating sequence and determine whether the problem involves the gas valve or another furnace component.

Contact SDG for Furnace Repair

If you suspect a bad furnace gas valve or your furnace starts but the burners won't ignite, contact SDG Duct Cleaning to schedule a furnace service call.

We provide furnace repair throughout Cornwall, Long Sault, Ingleside, Lancaster, Williamstown, Martintown, Apple Hill and surrounding SDG communities.

We're HVAC technicians—not just duct cleaners.