How to Repair a Furnace Gas Valve: Troubleshooting and Risks

Air Unlimited Heating & Cooling has been an established heating company in Liberty, MO, for over a decade. As a family-owned business, we bring personal experience and technical know-how, including how to repair a gas valve on a furnace.

A gas furnace, not surprisingly, needs a supply of gas and air for combustion to occur. The gas valve regulates the inflow of gas into the combustion chamber. Failure of the gas valve causes symptoms such as:

  • the furnace shutting down
  • the furnace failing to send warm air to the vents
  • an absence of the valve’s characteristic clicking sound

If your furnace is failing to produce heat and you don’t hear the sound of combustion, the gas valve may be responsible. It may be faulty, clogged, miswired, or unable to let gas in for some other reason.

The furnace gas valve is part of a complex system with many components that work together. To troubleshoot a gas valve, check each of these components for problems. Damage or wear to these components could point to the source of the gas valve malfunction.

What to Check If Your Gas Valve Isn’t Working

Pilot Light

Check to make sure the pilot light is on. If the pilot flame is too weak or keeps going out, the pilot safety valve could shut off the gas as a safety precaution.


Check the wires to the gas valve for frayed or damaged wires. The furnace is controlled electrically, so it will shut down if it loses electrical control signals.


If the thermostat is faulty, it might be shutting off the valve before the furnace has a chance to generate heat.


Air and gas are necessary for proper combustion. If the airflow is insufficient, improper combustion could release soot, carbon monoxide, and other dangerous byproducts. Check the ducts leading to and from your furnace for leaks or damage. You can also confirm that your furnace blower is set to the proper speed by referencing the furnace manual.

Gas Pressure

Gas pressure should come in between seven- and ten-inch water columns (meaning that the gas should have enough pressure to raise a column of water up that distance). The gas valve should reduce the pressure and allow 3.5-inch water columns to reach the burners. Check the pressure on the inlet-side port of your gas valve.


If the furnace is getting too hot, the evaporator coil may not be working correctly, causing it to shut off.

Circuit Boards

Check the circuit boards for damaged connectors or damage to the board itself. If the circuit board sends faulty or nonsensical signals to the valve, it could cause the valve to shut off. If your home is prone to electrical interference, we highly suggest whole-home surge protection.

Fixing Problems with the Gas Valve

As is evident from the list above, a problem with the gas valve could involve many other parts of the furnace. Experience and proper equipment are necessary to test each component to identify the culprit. There are many subtle signs, including sounds, smells, and the physical appearance of each component, that a technician uses to troubleshoot.

For most homeowners, it is best not to try to fix gas valve problems themselves. Unless you have experience in the area and know how to repair gas valves on a furnace, do not touch or try to fix the gas valve. This could lead to further damage and complicate the diagnostic process. A trusted repair technician will know best how to repair a gas valve or furnace.

If you see or hear anything that could point to a particular flaw, such as damaged wiring, make a note of it. If you observe unusual behavior in your furnace, such as the furnace coming on for a few moments and then shutting off again, note that too. Letting your technician know as much as you can about your furnace could shorten the repair time and reduce your bill.

 Your repair technician should be willing to listen to you and your experience with your furnace before diagnosing the problem or trying to fix it. If your furnace repair technician is not listening to you or treating you with respect, look for another heating and cooling company. You deserve a technician that takes the time to provide high-quality customer service.

Types of Gas Valves

Today’s furnaces use two different gas valves: combination valves and chain gas valves. Both accomplish the same essential functions, but their components are arranged in slightly different ways.

Combination Valve

Combination valves have been popular for home furnaces for nearly three-quarters of a century. They get their name from the electrical and mechanical components that combine within a single unit. The components of a combination gas valve include:

  • A manual shut off valve that allows you to physically disconnect the gas supply in an emergency
  • A regulator that controls the gas pressure
  • A solenoid valve controlled by the thermostat to regulate heat
  • A pilot safety that shuts the gas supply off if the flame goes out

Chain Gas Valve

A slightly different type of valve, the gas chain valve, includes the same three switches, the thermocouple, the solenoid valve, and the pilot safety valve. The main difference is that they are separate and hooked together in a series (or “chain”).

The components of a gas valve work together in preventing gas leaks, damage to the furnace, or even explosion. Before attempting furnace repair, remember that safety is paramount.

Heating Services from Air Unlimited Heating & Cooling

Air Unlimited offers 24/7 emergency services as well as residential and commercial services. In addition to knowing how to repair a gas valve on a furnace, Air Unlimited Heating & Cooling handles installation, repair, and maintenance of heating, cooling, and HVAC systems. Protect your home and family from the dangers of a faulty furnace. Call (816) 286-7258 to schedule a service call today about furnace repair by Air Unlimited Heating & Cooling.