How to Replace a Gas Valve on a Furnace

Your gas valve controls the gas flow into your heating system, but what do you do if the valve doesn’t work well? Knowledge is power, so you may want to know how to replace a gas valve on a furnace.

We provide expert heating services in Waddell, AZ, and wouldn’t suggest you replace the valve without experience. However, learning some HVAC maintenance details can help you make better property care decisions.

Reasons You Might Replace a Gas Valve

Gas valve troubleshooting is a potentially dangerous process, but anyone can identify the need for a gas valve replacement without serious health concerns:

• Inadequate heating or a lack of heat
• Strange noises, like rattling, banging, or hissing
• A strong smell of gas near your heating unit
• The pilot flame or other flames putter out or don’t light up

A faulty gas valve could lead to a gas leak. Have someone address the situation quickly if you think the valve isn’t working.

Signs It’s Not the Gas Valve

People with inexperience often misdiagnose heating issues. Our team could find that the gas valve is unrelated to your HVAC issue or is only part of the problem.

Circuit Burnout

The wires connecting to different furnace parts can burn, fray, or crack. Electrical power flowing through those broken wires may smell odd or prevent the flames from igniting. You wouldn’t need to know how to replace a gas valve on a furnace for this.

Blocked or Plugged Burners

Your system’s burner orifices shouldn’t have any dust, soot, or grime blocking them. We test the pressure of the gas leaving the valve to ensure it is around 3.5” WC (inches of water column). If the pressure is too low, try cleaning the orifice first.

Flame Sensor Replacements Needed

Your flame sensor indicates whether or not the flame for your furnace is on. Once a flame ignites, the sensor should indicate that and keep your furnace running. However, if it doesn’t notice a flame, it will shut the system down to prevent gas leaks.

What if the pilot light or other flame comes on when you use the furnace ignition system, but it doesn’t stay on? You may need to replace the flame sensors instead of replacing or adjusting a furnace gas valve.

Simplified Steps for Replacing a Gas Valve

We follow stringent safety precautions and valve replacement steps each time we do a job. Although simplified, these can give you an idea of how to replace a gas valve on a furnace.

#1. No More Power

Turn off the power to your heating system from the circuit breaker. Keep it off for the whole process.

#2. No More Gas

Turn the gas pipe’s shutoff valve counterclockwise until it hits the backstop.

#3. Shut Off the Electricity

Unplug all electrical components inside the system to prevent sparks. You may need to remove or loosen screws and pull wires connected to the gas valve.

#4. Pop the Union Fitting

Use two adjustable wrenches, one to hold the gas pipe’s union fitting and another for the union nut. Turn the second wrench until the nut comes off.

#5. Rotate the Intake Pipe

While holding the gas valve still, turn the intake pipe counterclockwise. Then, move it out of the way.

#6. Remove the Old Valve, Ready the New One

Holding the gas pipe connected to the valve’s output, turn the old valve counterclockwise until it comes off. Then, ensure the new valve’s identification labels match the old one. A poorly fitting valve won’t work.

#7. Apply the Pipe Thread Compound

Pipe thread compound helps prevent gas leaks. Don’t put so much that the compound spreads onto the inside of the pipe, though.

#8. Work In Reverse

Work backward from Step 6 to Step 1, putting on the new valve, replacing the intake pipe, and everything else. If you had to turn something counterclockwise to remove it, turn it clockwise to put it back on.

#9. Leakage Check

After a gas line disconnect, you need to make sure there are no new cracks or leaks in your pipeline. Check for gas leaks and adjust the system to meet pressure requirements.