Washing Machine Basics - How They Work

Tub (or inner tub)

Where you put the clothes. In most washing machine brands, this tub has hundreds of small holes that allow the water to flow through to an outer tub. The outer tub is solid and holds the water. For top loaders there is an agitator at the center of the inner tub. Front loaders spin and allow gravity to do the work as the clothes tumble and bounce, so do not have agitators.

Central agitator

The agitator on top loaders pivots clockwise and counterclockwise--about three-fourths of a revolution--plunging the clothes through the water to wash them. The clothes keep moving from the top of the tub down to the bottom and back again. This motion allows the detergent and water to reach every part of the clothing and loosens the soil. Agitators are not present on front load machines.

Motor and pump

The motor drives the agitator in a top loader or creates the clothes movement in front loaders during the wash cycle and spins the clothes during the damp dry or spin cycle. The pump removes the water from the tub and lifts it out to the drain.

Fill valve

The fill valve--which is about the size of a coffee cup--is sometimes also called a "water inlet valve." It controls the entry of hot and cold water into the machine. The valve has three major components: a hot-water solenoid, a cold-water solenoid, and a mixing valve body. The inlet or fill valve is where the hot and cold water from the house are hooked up to.

Timer and selector switches

  • Timer switch is usually the largest dial on the main control panel. It can be either a mechanical device much like a simple clock, or completely electronic with just a digital readout. The timer runs in a pre-determined pattern, providing electricity to all of the washing machine components at the correct time and for the correct length of time.The Start switch is usually part of the timer knob. When you set the timer to the proper cycle, you either pull or push the timer knob to start the cycle.
  • Selector switches or knobs vary from machine to machine. These let you adjust certain settings; for example, the water temperature, spin speed, timer cycle, and so on. Normally, the washing machine completes the cycle selected on the timer, regardless of how you set these switches and knobs.

Clutch and brake mechanism

Motors can start up and reach full speed in a second or less, which is too fast for many of the components the motor drives. So most washing machines use an automatic clutch to dampen the effect of the motor starting up.

  • On some washing machines, the clutch is just a combination of the drive belt slipping temporarily on a pulley and gradually tightening. On other units, the clutch is more like one you would find in a car--it uses a drum-and-pad combination of components.
  • When the lid is raised on a top-loading washing machine, some functions cease. On all machines the spin cycle stops, which brings the drum to a rapid halt. Many units use a special braking mechanism to stop the spinning inner tub. It is similar in design to the brakes on a car.

Motor coupler and/or belt

A few types of washing machines use a coupler to connect the motor directly to the transmission. It makes the connection without the need for a belt. The coupler is a rubber disc ½ inch thick by 1-½ inches in diameter, sandwiched between two plastic sprockets. Many other washing machines use belts to connect the motor to the transmission or pump. A belt is a black, rubber, continuous rope-like component--usually a loop of about 24 to 30 inches.

The belt provides a desirable "weak link" in a washing machine. That is, if the tub or agitator were to become stuck or jammed, the belt is more likely to fail, which would preserve the transmission and other critical components.

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