How to Test a Gas Valve Solenoid Coilby Chris Stevenson
The solenoid opens the gas valve to feed the flame when you turn on a gas furnace or gas-heated clothes dryer. It closes the valve when you turn off the appliance. The solenoid opens the gas valve when a glow stick gets hot enough to ignite the gas, which turns the burner on. The forced heat from the burner dries the clothes in the dryer tumbler, or warms the air in the furnace. Any homeowner can check his valve solenoid coils, using some up-close visual observation. With the help of an assistant and a multimeter, finding the problem can be relatively easy.
Unplug the appliance from the wall outlet. Turn off the gas feed line valve to the dryer. This valve is usually found in the wall line leading to the dryer, and is shut off by turning the handle perpendicular to the gas line. Locate the front, lower access panel to the appliance. Most gas dryers have pullout snap panels. For a furnace, the lower access panel will remove from the front, or the side. Push a screwdriver in the seam of the lower pane, in the case of a gas dryer, and pry the lid off the plastic snaps. Use a screwdriver to remove the sheet metal screws on a furnace or other appliance.
Use a flashlight to inspect the interior of the burner assembly. Sweep out any hair, lint and foreign debris with a feather duster. Locate the gas valve mechanism, which looks like a small metal device that has two coils attached to it. Have an assistant plug in the appliance and turn on the gas feed valve. Have the assistant set the dryer for high heat and turn the dryer on. Watch the small tip of the igniter, which should glow bright orange when heated.
Watch the igniter tip and count the seconds while it remains on. If after 15 seconds or so it fails to ignite the burner and goes out, the problem points to a solenoid coil failure. If the igniter lights the burner, which burns blue steadily for several minutes, but the igniter fails to shut off and remains on, the problem points to a failed flame sensor. The correct sequence should be: Igniter glows, burner ignites with a steady blue flame and then the igniter goes off.
Unplug the appliance from the wall outlet. Turn off the gas feed line valve. Locate the small wire jack that attach to the coils. You might have one wire jack and one coil or two wire jacks and two coils. Depress the plastic snap connectors on the wire connectors and pull them free. Set a multimeter to probe on one of the male tab terminals on the coil and the other multimeter probe on the opposite terminal of the same coil.
Set the multimeter to the ohms-times-10 setting. Read the gauge. The reading should change from infinity to approximately 1,300 ohms, plus or minus 150 ohms, when the probes contact. If the reading shows infinity or deviates too much from the 1,300 reading, it indicates a defective valve solenoid coil. If you have two coils, test the other in the same fashion by placing the multimeter probes onto each male terminal.
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