The gas valve in a furnace controls the incoming gas supply that fuels the heating process. The valve helps ensure that the furnace only receives the gas it needs, which prevents energy losses and potentially hazardous gas leaks. If the valve stops operating correctly, your furnace could quickly stop heating at all.
Did you narrow the problem down to the gas valve through troubleshooting? Removing and replacing the part isn't difficult though you should always feel comfortable calling in a heating contractor to perform the task instead. The process starts with removing the broken gas valve from your furnace.
What You Need:
Step 1: Remove the Gas Valve from the Furnace
Turn off the electrical and gas supplies to the furnace using the circuit breaker and shut-off valve, respectively. Locate the upper furnace's upper access panel and determine if it has any fasteners holding it in place. Remove or twist any fasteners, if needed, then lift the panel off the furnace and set aside.
Use two wrenches to separate the gas supply pipe union. Place one wrench on each side and twist one while holding the other steady to separate the pipes from the junction. You can finish the unhooking by hand once the junction has loosened; note that you don't need to remove either pipe but merely need to separate the pipes. Unthread the inlet pipe from the gas valve using a wrench.
Use pliers to disconnect the connector ends of the wires attached to the gas valve. Use a screwdriver to unthread the mounting screws on the gas manifold, which should sit below the gas valve. Pull the manifold and the gas valve assembly free of the furnace and set on a flat surface so that you can finish removing the valve.
Step 2: Remove the Gas Valve from the Manifold
Unthread the gas valve from the manifold using one wrench on the far end of the valve and the other wrench on the manifold. Twist the far wrench while holding tight to the one on the manifold. Note that you might have to use some force to get the valve to unthread entirely from the manifold.
Your furnace unit is now ready for the new gas valve. If you aren't ready to install the part yet, put the access panel doors back on the unit but don't restore the electric or gas supplies. For more information, contact companies like Ronnie Ritchie Service Co Inc.