How Does a Dishwasher Work? | Dishwasher Diagnosis

How Does a Dishwasher Work?

A dishwasher combines water with detergent, heats the mixture and sprays it against the dishes. It pumps out the dirty water and then rinses the dishes with clean water mixed with a rinse agent. After pumping out the rinse water, the dishes are dried by either heating or air drying them. The selector switch allows you to pick a variety of cycles which vary the length of wash, water temperature and drying temperature.

When the door latch is closed, the door switch is engaged and allows the dishwasher to operate. Based upon the chosen cycle, the selector switch signals the various components to operate at the appropriate stage of the cycle. The timer regulates the length of each stage of a cycle.

The water inlet valve fills the tub with water. A float in the tub prevents the dishwasher from overfilling. Either the float or the timer signals the inlet valve to close. The detergent is then released into the tub. In many dishwashers the mixture is heated with an electric heating element. Water that is not warm enough results in poor cleansing.

The motor turns a pump which forces the water up through the spray arms and spray tower (if any). The pressure of the water causes the arms to turn.

Some dishwashers have a two-way motor. When it turns in one direction, it pumps the water through the spray arms. When it turns the other way, it pumps the water out through the drain. If the motor only turns in one direction, then an actuator moves to channel the water either to the spray arms or to the drain.

After the detergent cycle is complete the dishes are rinsed. If the dishwasher has a rinse agent feature, the rinse agent is added to the rinse water.

Once the rinse cycle has completed and the water has been pumped out, the dishes are dried. A electric heating element heats the interior of the dishwasher. Some dishwashers also have fan to circulate the air. A thermostat prevents the dishwasher from overheating.

Some dishwashers employ soil sensors to monitor the clarity of the wash water. When the water becomes clear, the sensor signals the control timer to advance to the next cycle.

Dishwasher Troubleshooting Tool

In order to diagnose a problem with your dishwasher, it helps to list the symptoms and narrow down the possibilities. The following table contains a list of common symptoms for a malfunctioning dishwasher. Locate the symptom your appliance is exhibiting and to the right is a list of some possible causes.

The same cause may have multiple symptoms, so if you find the same cause for multiple symptoms of dishwasher, that is a good place to start. In general, the causes are listed in the order of the ease of testing / repair or the likelihood of it being the cause of the problem.

Many of the suggested tests link to an article on how to conduct the test or how to make the repair. Also, if we don’t have an article posted, be sure ask your questions at our Appliance Repair Forums.

Symptom	Check Click on underlined items for further information
Dishwasher does not work – no sound, water or lights	· Check for a blown fuse or tripped circuit breaker · Check that the dishwasher is plugged in securely or · Inspect the wiring connection to the dishwasher for burns or breaks. · Check the door latch · Test the door switch · Test the timer motor · Test the selector switch · Test the motor start relay · Test the motor
Dishwasher does not start but motor hums	· Unjam the motor · Unjam the pump · Test the motor · Test the motor start relay · Check the drive belt
Dishwasher does not fill with water or it drains while filling	· Check that the water supply is turned on. The valve may be located under the sink. · Check the door latch · Test the door switch · Inspect the float assembly · Inspect the fill tube for kinks · Test the float switch · Check the inlet valve filter screens · Test the water inlet valve · Test the drain valve lever arm · Check the drain valve
Water does not drain from the dishwasher	· Check sink drain and drain hose for restrictions · Unjam the motor · Unjam the pump · Check the drain valve · Check the drive belt · Test the timer motor · If you have a brand new dishwasher or garbage disposer, check the knock out plug on the garbage disposer.
Dishwasher is leaking water	· Inspect the seals for the main tub, float, heating element and blower diffuser · Check for overfilling · Inspect the water and drain hoses · Inspect the door gaskets · Check the water inlet valve · Check the pump

Water or soap leaks around the door	· Make certain that your detergent is intended for dishwashers. Do not use liquid dish soap. · Inspect the door seal gasket · Check the door latch · Inspect the door hinges · Inspect the spray arms for damage
Water drains through the air gap into the sink	· Check the air gap
Dry cycle problems	· Test the heating element · Test the drying fan · Test the thermostat
Dishwasher is noisy	· Check the spray arm for damage and obstructions · Check the inlet filter screens · Test the water inlet valve · Check the motor and mounts · Check the fan motor and blade · Check the drain for obstructions
Door drops down with too much force	· Check the door springs
Door does not close or latch properly	· Check for obstructions · Check the door latch · Inspect the door hinges · Inspect the door seal gasket
Dishwasher cycle does not complete	· Test the timer motor · Test the thermostat · Test the heating element
Detergent cup does not open	· Check the detergent cup for obstructions · Test the timer motor · Check actuator arm · Test the bimetal assembly
Cycles times are too long	· Test the timer motor · Test the heating element · Test the thermostat
Dishes are not cleaned adequately	· Check for adequate water level · Check the spray arms and spray tower · Check the water temperature · Check the detergent cup · Clean the fine particle filter · Check the inlet filter screens · Check the water pressure · Test the water inlet valve · Check the drain valve · Test the selector switch · Test the timer motor · Test the heating element · Test the bimetal terminal assembly
The walls, racks or tub are rust stained	· Scrub the interior with oxalic acid · Repair the exposed metal

How To Choose a New Dishwasher

Things to Consider when Choosing a Dishwasher:

When it is time to choose a dishwasher, whether for a new installation or a replacement, there are many things to consider besides price and appearance. Features, reliability, and usability are really more important. Because when it comes down to using the dishwasher, no matter how cheap or pretty it is, if your dishes don’t fit or if they don’t get clean, it wasn’t a good buy.

There are many high-end dishwasher models out there. They might seem the best choice, but they don’t always do any better than lower priced models. Do your research on quality and results. Read forums, and reviews to get other peoples opinions on the products you are considering.

When shopping for a dishwasher, look at features and consider which really matter to you. Here are some recommendations we believe will help you to choose your next dishwasher.

Rack configuration– Some racks are better with some dishes than others. Adjustable tines will allow more versatile loading. If you have a problem dish, bring it along when shopping to make sure it fits.
Drawer models– Newer to the market are dishwasher drawers. Typically you get two drawers that stack one over the other and occupy the same space as a conventional dishwasher. You can operate one drawer independently from the other. They are more expensive and generally are less versatile for loading but may be more economical for small loads. We think they are trendy but not a good bang for your buck.
Noise level– Most newer models are much quieter than those made just a few years ago. Some models are so quiet you may not be able to tell if they are running just by listening. A quiet dishwasher is a nice plus when trying to work, or talk in the kitchen.
Hidden or exposed controls– If you want to reduce the appliance clutter in your kitchen you might opt to install a cabinet panel on your dishwasher to make it blend in with the cabinetry. Even without a cabinet panel, you may find hidden controls more attractive. Also, hidden controls reduce the risk of small children playing with the dishwasher controls.
Heating element– European models typically have no bottom heating element and so must air dry. They may circulate heated air, but you will still have to add rinse aid to prevent spotting.
Stainless steel interior– A stainless interior should not rust, may be more attractive and may resist staining. However, you must not use any bleach based detergents or cleaning products to avoid damaging the surface.
Energy Star rating– Many dishwashers are Energy Star rated, meaning they use less energy. Some communities may even offer a rebate for choosing an Energy Star appliance.
Programs or cycle settings– Choose a model that has the settings you really need. A model with many settings may be irrelevant if you never use them. A delayed start feature is useful to start the dishwasher when you are away or asleep.
Will you pre-rinse?– Some models offer heavy-duty food grinders that reduce the risk of clogging from food particles. Some models require a pre-rinse while others do not.
Appliance size– Whether replacing or adding a new dishwasher, make sure the new dishwasher will fit in the opening. Most models are 24 inches while some 18 inch models are available.

Dishwasher Tips and Advice

Do:

Buy detergent in a size that you can use in 30 days. It works better when fresh.
Scrape the dishes, but no need to pre-rinse (unless there is dried on food).
If you have hard water use more detergent.
If you have hard water use a rinse aid.
A water temperature of at least 130 degrees is needed for the best results.
If your dishwasher doesn’t heat the water, run the hot water in your sink before starting the dishwasher to get more hot water to your dishwasher when it is filling.
Heated dry is more sanitary, but air dry is more energy efficient (you decide)
Once every two months, run an empty load and add two cups of white vinegar to dissolve hard water deposits.
Clean the filter at least once a year.

Don’t:

Don’t ever use dish soap, it will oversuds and make a mess.
Don’t use gel soap, it tends to gunk up the system.
Don’t overload the dishwasher, it won’t clean as well.
Don’t bother to pre-rinse dishes unless there is dried on food.

How To Load a Dishwasher

If your dishes aren’t clean enough after running them through the dishwasher, you might get better results by changing the way you load the dishes. Here is how to get your dishes their cleanest by optimizing dishwasher loading.

While poor cleaning can be the result of problems with the dishwasher itself, loading the dishwasher improperly can also lead to dishes not being clean enough. To get the cleanest dishes, follow these tips.

Load dishes with dirty side toward the center
Do not nest dishes, make sure there is space between each dish for water to spray the entire surface
Place large objects toward the back to avoid blocking soap and spray
Load silverware handles down, except knives load handles up for safety
Spread spoons and forks around the silverware holder to prevent nesting
Load glassware and delicate items on upper shelf
Place large utensils lying on the upper tray, place them on their edge if possible
Don’t over load the dishwasher, do two loads instead if there isn’t plenty of space for the water to reach everything

The key is that the spray of water should be able to reach the surface of ever dish. When too many items are washed, or items are packed too closely together, the spray can be blocked which prevents thorough cleaning.

Another factor affecting how clean your dishes turn out is the water temperature. Hot water is important for scrubbing dishes clean. Some dishwashers will heat the water first, while other models just use your home’s hot water. In the latter case, the first few seconds of water are usually not hot at all. If your dishwasher doesn’t preheat the water, you should turn on the hot water at your sink and wait until it is fully hot before starting the dishwasher. That way the water entering the dishwasher will already be hot enough for cleaning the dishes.

The detergent used can affect your results too. Some detergents don’t dissolve well, especially if the water isn’t hot enough. Some gels and tablets don’t dissolve fully, making them less effective. If you open your dishwasher mid-wash and find undissolved detergent, consider trying another brand of dishwasher detergent.

Finally, most dishwashers have a filter to capture glass and large particles. Regularly remove and rinse the filter to allow the rinse water to quickly flow out of the dishwasher. If the filter is partly blocked, food particles will also begin to build up which will cloud the rinse water and reduce the cleaning effectiveness of your dishwasher.

What to do if the Wrong Soap was Used

So you used dish soap instead of dishwasher soap? If you did, you know the result; lots and lots of soap suds that just won’t stop. So what do you do?

This is easy to fix, if you know what to do; and we do. First scoop out as much water as you can and dump it in the sink. Next add a cup or two of white vinegar and run the dishwasher for a short time. Now scoop out more water.

The vinegar cuts the foaming action of the soap. You may have to repeat the process to eliminate the suds because some soapy water remains inside the pump and hoses.

Also, if you poured it into the soap dispenser, wash that out by hand to get all the dish soap out.

How Does a Dishwasher Work? | Dishwasher Diagnosis

How To Choose a New Dishwasher

Things to Consider when Choosing a Dishwasher:

What to do if the Wrong Soap was Used

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