A pressure switch, also called a water-level switch, monitors a washing machine's water level. Once water reaches a certain level in the wash tub, the pressure switch triggers and alerts the control panel to close the water-inlet valve. If you're experiencing problems with water over or under filling your washing machine, it's likely due to a pressure-switch malfunction.
How It Works
A long, plastic, air-filled tub extends from the pressure switch near the top of the outer wash tub and the control panel to the base of the machine. When water fills the tub, it also enters the tube at its bottom end and pushes air up toward its top. Eventually, the water reaches a level that causes a build-up of air pressure that's great enough to activate the pressure switch. Once initiated, it signals the control panel to close the water-inlet valve, so water stops filling the tub.
Troubleshoot Water-Fill Problems
If the pressure switch fails, it can disrupt wash cycles. In particular, a broken pressure switch can cause a washing machine to overfill and for water to spill out of the machine. It can also cause the water-inlet valve to close prematurely, so water never reaches a certain level. Always check the integrity of the pressure switch when you experience irregular water fill in your washing machine.
What to Look For
Consult your washing-machine manual for guidance on how to locate the pressure switch on your specific appliance. After you've located it, evaluate it for defects. Run your fingers over the length of the tube and feel for any kinks or cracks, either of which warrant a tube replacement. Also, make certain the tube doesn't hold any water and it's attached to the bottom of the outer tub as well as the pressure switch. If it's not connected, reconnect it or call a repair technician to repair it. When water lingers in the tube, it usually indicates there's a breech and the tube requires replacement.
Always shut off power to the washing machine before initiating the troubleshooting process to prevent electrical shock. Drain the washing machine manually of water before attempting to locate the pressure switch. If you can't identify a problem with the switch, a clogged drain line or water pump can also interfere with a wash tub's water level.