How do Washing Machines Work?

Washing Machine Filling with WaterAny attempt at fixing your washing machine yourself will be helped greatly by a basic understanding of how this major appliance works. Most everyone knows that washers go through wash and spin cycles, but as not so clear on the details of what goes on inside to run them.

Also, the exact design will differ among manufacturers and models, but there are some things all washers share. They all have electric motors driving the action, some way of draining and filling themselves with water, and timers to control the activation and stopping of the different cycles, for example.

Fill Cycle

The fill cycle is the first thing that happens when you start the washing machine. A water mixing valve is opened by a solenoid actuator, allowing cold or hot water, to enter the tub area. There is usually one valve for hot and one cold water in the same dual-valve unit, and when warm water is used, both valves can be opened to mix cold and hot.

The tub is filled strictly from the pressure in the house plumbing supply lines and a water pump is not used. The hot water also comes from the hot water supply lines in the house, rather than being heated from something in the washer.

The water solenoid valve will be tripped to shut off the supply when the water level in the tub reaches a sensor placed at the fill level. The sensor may also be a pressure switch or, more rarely, water weight switch.

Wash and Rinse Cycles

The water valve is now closed, and the electric motor is started. The motor drives a belt, which drives a transmission, sometimes with a clutch mechanism. The transmission is used during the agitation cycles to convert rotary motion to back and forth motion. A drive shaft extending from the transmission is connected to the basket holding the clothing articles as well as the agitator.

In a front loading machine, an agitator is not required, since the horizontal axis of basket creates a natural agitation of the contents through gravity, as the clothes rise to the top of the basket then fall to the bottom.

A timer controls the length of the agitation washing cycle. In some models, a pump, driven by the main electric motor, is used to re-circulate the water from the bottom of the tub to the top through a hose. Also during this cycle, softener or bleach may be automatically released into the tub, via a solenoid activated valve which opens the dispenser; this action is also controlled by the timer.

Spin and Drain Cycles

Next are the spin and drain cycles, typically these are combined into one. In the drain cycle, a pump pumps all the water from the tub into a hose connected to the house drain plumbing line. In the spin cycle, the electric motor drives the basket at high speed in order to remove excess water from the clothes through centrifugal force. So that the clothes basket will speed up slowly, it is engaged to the drive shaft gradually via a clutch; this prevents putting undue stress on the drive train.

There are various safety mechanisms which prevent accidents during the high-speed spin cycle; there are lid switches which can kill the motor when the lid is opened, lid or door locks that prevent the machine from being opened during the spin (or all) cycles, and a braking mechanism to stop the basket from spinning at the end of the spin cycle, or if the lid is opened. The purpose of all these is to prevent someone from inadvertently putting their arm or hand into the spinning basket, which could cause severe injury.

Now What?

Your task when troubleshooting a broken washing machine will be first of all to determine during which of these cycles the problem is occurring, then to figure out if it is a mechanical problem or electrical/electronic problem, then finally to isolate the actual faulty component. If your unit is a washer dryer combo, there will be another area to look at, the ventilation and heating aspects of the dryer.

As modern control electronics are fairly reliable and robust, the most common problems occur with the mechanical components such as the pump, motor and transmission, and manifest in problems like overfilling, failure to properly drain, or the machine not spinning.

Your best bet is to find a good appliance repair service, but if you know of a good appliance parts dealer in your area, sometimes you can get good troubleshooting advice from the counter persons. If you go that route, you should know the above basics and have the following information with you: the manufacturer’s name, the name of the model, and the serial number from the machine’s nameplate.

You can find the nameplate in one of these locations- inside or underneath the lid, on the back panel of the machine, on the bottom of the front panel in one of the corners, or on the side or top of the console area where the control dials and buttons are located.

If you cannot find the nameplate, and do not know the model number (check the paperwork that came with the washer when you bought it), then bring the suspected faulty part with you to the appliance dealer or parts shop; they sometimes will be able to trace the part number to the model number or if they are really good, they will know what machine it came from just by looking at it.

See Also: Tools for Fixing a Washing Machine

Photo by Viewoftheworld, Creative Commons Attribution License