How To Replace The Gas Valve On A Gas Furnace That Suddenly Stopped Heating

19 April 2016
 Categories: , Blog


Has your gas furnace recently stopped heating despite the fact that the pilot light is lit and the burner is working properly? There could be a malfunction in the unit's gas valve, which controls when the gas supply enters the furnace based on whether or not the pilot lit is on. If the valve stops working, no gas will enter, and your furnace will lack the fuel it needs to heat your home.

Replacing the gas valve isn't difficult but bear in mind that failure to properly secure the new valve or the associated piping could lead to a potentially dangerous gas leak. If you have any doubts in your abilities during the project, stop what you are doing and call in a furnace repair technician.

Things You Need:

  • Screwdriver
  • Pipe wrenches
  • Small knife
  • Socket wrench
  • New gas valve
  • Plumber's sealant
  • Zip tie

Step 1: Gain Access to the Gas Valve

Turn off the electricity to the furnace at the circuit breaker and the gas supply using the shut-off valve on the supply line hooked to the furnace.

Locate the access panels on the rear of your furnace and determine how the panel doors are held into place, which is usually either with screws or knobs. Use a screwdriver to remove the fasteners to the lower access panel or twist the panel door's knobs to release. Pull the door away from the furnace and set aside.

Use a set of pipe wrenches to separate the gas supply pipe union. Finish loosening the union by hand and then pull up on the upper pipe to separate the segments. Let the upper pipe rest in place next to the lower pipe.

Step 2: Remove the Old Gas Valve

Locate the gas valve inside the furnace area opened up when you removed the access panel door. Use a pipe wrench to unthread the inlet pipe from the gas valve; it might be easier to finish the unthreading with your hand.

Disconnect the wires attached to the gas valve. There aren't many wires so you don't need to worry about memorizing the orientation. Disconnect the grounding wire below the gas valve. Use a small knife to cut the zip tie bundling the other valve wires together.

Use a socket wrench to remove the mounting screws holding the gas valve and manifold onto the burner housing. Now you can pull up on the entire gas valve assembly and remove the assembly from the furnace.

Use a pipe wrench and your hand to unthread the gas valve off of the manifold pipe.

Step 3: Install the New Gas Valve

Remove the new gas valve from its packaging and pull out its inlet and outlet plugs, if needed. Apply a thin, even layer of plumber's sealant to the pipe threads on the end of the gas valve manifold. Twist the outlet port of the new valve onto the manifold pipe using your hand then a pipe wrench. Make sure the valve's final orientation is pointing in the same direction as the original valve.

Align the valve assembly into the furnace using the orifices as a guide to line the assembly up with the burner tubes. Use a screwdriver to replace the mounting screws to secure the assembly.

Reconnect the grounding wire below the valve assembly. Connect the individual wire ends to the appropriate terminals on the gas valve. Bundle up the ends of the wires and secure together with a new zip tie. Check to make sure that the gas valve is turned on and turn on, if needed.

Apply a thin, even layer of plumber's sealant to the thread on the gas valve pipe then thread that end into the side of the gas valve assembly. Realign the gas pipes on the side of the furnace and secure the union connector using your pipe wrenches.

Put the lower access panel door back on the furnace and secure the door into place using its screws or knobs. Turn on the gas supply and electrical supply. Test run your furnace to see if the problem is still occurring and call a furnace repair company for further help, if needed.  

For more information, contact One Hour Heating & Air Conditioning or a similar company.