Dishwasher Not Cleaning

Autor:in: nicO (und 4 andere Mitwirkende)

Dishwashers have one job — eat dirty china and silverware, and spit out clean dishes. When your dishwasher isn't cleaning properly, the top rack isn't clean, or becomes clogged regularly, here are steps to get it running normally again.

If your lower rack is clean, but the upper rack is dirty, jump to failed diverter motor.

Another similar issue is a smelly dishwasher. Follow that guide instead if the problem is more applicable.

Make sure your detergent is compatible with dishwashers. Do not use liquid dish soap, as your machine will become foamy and sudsy before overflowing.

The inlet valves allow water to enter the dishwasher. When clogged or failing, either not enough water will enter the machine for a proper cleaning cycle to run, or the machine will continue filling with water until a leak or overflow occurs. If you're experiencing these issues, the water inlet valve may be at fault.

Since the valve can fail both electrically and mechanically, test its continuity. Continuity confirms that an electrical path is present, and what its resistance value is. If the water inlet valve continuity tests at around 500-1500Ω, then it's likely fine. If it tests Overload (OL) or off the charts, it needs replacing.

After verifying electrical continuity, turn off hot and cold water supplies to the dishwasher. Then, disconnect the water supplies to the inlet valve and hold the hoses over a sink or water basin, or bucket. Turn the water supplies on and see that water is flowing strongly at a reasonable pressure between 20-120 psi and not dribbling out. A low pressure and weak flow suggests issues with the water supply lines, or valves. If the flow is strong, remove the valve and fill hose, and replace with a new water inlet valve.

Note: Do not attempt simply cleaning and replacing a clogged valve as this part is likely to fail after disassembly.

The spray arm may have become clogged with food particles. Unclog the holes, and wash with soap. Make sure to clean both upper and lower spray arms. Check the spray arm gaskets and replace if necessary.

If the wash arm is cracked, a stream of water can spray the door seal and cause a leak. Inspect and replace the wash arm if there is a crack. Do not fix the crack with glue as the glue will break down inside the machine. Epoxy will work as long as it can handle the internal run temperatures (120°F - 180°F).

If the wash arm is intact, check that the support screws are tight. Looseness may allow water spray between the wash arm support and the pump housing, and thus another leak.

The drain hose transfers fluid from the bottom of your dishwasher to your garbage disposal or under sink drain connection. Solid debris — food, hair, etc — can accumulate in the drain hose with time, but clogs normally form with broken plastic, stickers or porcelain chips.

Check for a kink in the drain hose that runs from the bottom of your dishwasher to the drain pipe (usually below the sink). Make sure it’s not pinched or kinked. If necessary, replace it with a new hose.
Check for a clog. Remove the drain hose end from the nipple it's connected to below the sink or disposal, put the end in a bucket, then fill and drain the dishwasher to see if a garbage clog will simply blow out.
If that doesn't work, but you see a small dribble of water, you may have to pull the dishwasher out and remove the drain hose in order clean it out or replace it.
- Remember, there's still water in the unit—so put a drain pan under it before removing the hose.
Remove the sump pump screen at the bottom of your dishwasher and remove any materials that shouldn't be there. This screen is usually held in by a couple of screws. Remove the coarse and fine filters and remove all foreign material.

The diverter motor aligns the diverter disc so the disc can direct water through the upper spray arms. If the diverter motor fails, the dishwasher will stop and throw an error code. The seal is the gasket around the diverter motor shaft where it meets the bottom of the sump. A leak will damage the motor and leak beneath the machine.

Safely uninstall the dishwasher and tilt it on its back.
Remove the diverter motor and seal. The shaft may be worn which caused the seal failure and leakage. Inspect the switch printed circuit board (PCB) inside for corrosion, and replace if necessary to prevent future seal failure.
- Consider applying clear nail polish, conformal coating spray, silicone, or RTV to waterproof the board during installation.
Install a new diverter motor and seal. Lubricate the seal and diverter shaft with plumber's silicone faucet lube.
Replace the red wire diverter connector. If it's corroded and not replaced, the diverter will spin continuously and result in early seal failure.

A new drain pump should only take a few minutes to remove all water from your dishwasher. Taking longer to remove the water or leaving standing water in the machine is a sign of a bad pump. Low humming or squealing noises also point to a pump problem. Pumps can fail both electrically and mechanically. Some models of dishwashers may have separate pumps to drain and circulate the water, so check both pumps. These pumps are normally on the bottom of your dishwasher.

If your the dishwasher adds water, heats, and empties water, but the dishes are not clean then the circulation pump is likely the issue.

Let's listen to our dishwasher.

A loud buzzing noise indicates a blocked or dirty drain pump or wash pump. If the pump is jammed, remove the blockage. You may have to replace the drain pump if there are no blockages.

A squealing or droning suggests a failing wash pump. Search for blockages to the pump, and replace the wash pump.

A scraping sound suggests a damaged impeller or impeller fin scraping against the pump housing. The impeller is inside of the pump and is what moves the water through the system. Replacing the impeller instead of the whole pump may be possible. Inspect the impeller. If it's broken, replace it.

Often, you can find a blockage by removing the filter and fishing around the drain hole with your finger. Be careful, as some blockages can be sharp.

Remove the blockage, clean the filter and put the filter back.

A worn drain pump may also have a hole, crack, or worn bearings causing a leak. Replace the drain pump in this case.

If none of the above tones are evident, then disconnect the drain pump from the system, and test its continuity. If the measured impedance in Ohm (Ω) between terminals is 15-40Ω, your drain pump is likely fine.

If the pump just hums when it should be running, the entire pump assembly might need to be replaced.

There are many parts of the dispenser that could fail, and prevent soap from reaching the washing chamber. Taking apart the dispenser and testing the bi-metal actuator for continuity could show a faulty part. Use a multimeter set to Ohm (Ω) and check for continuity by placing the probes onto the electrical leads. If the bi-metal tests outside of 0-1Ω, try this quick fix for the thermal fuse. Apply a drop or two of WD40 on the plastic hooks that hold the fuse in place, then slide it to the side and unhook. Remove the connectors, place the fuse in a plastic bag and leave it in the freezer for a few hours. Smack the fuse on a counter or hard surface. If it reads between 0-1Ω with a continuity test you can continue using the part. Otherwise, replace bi-metal actuator with a new part.

In the event that the dispenser is not opening, you can replace the entire dispenser instead of troubleshooting and replacing individual actuator, door pin, spring, latch, lever, lid, or slide.

Remember, the water temperature should be 140 to 150 degrees Fahrenheit as it enters the dishwasher tub.

Check the water temperature at the closest faucet. Let the water from the hot water tap run before starting the dishwasher to clear the water line of any cold water.

Not enough detergent for the degree of water hardness or for the amount of dirty dishes to be cleaned.

Use 1 teaspoon of detergent for each grain of hardness, with 3 teaspoons of detergent, at a minimum, in soft water. The dishwasher will require extra detergent for greasy pans.

Improper loading of the dishes into the dishwasher.

Blocking the spray nozzle. If a large bowl or pot is placed over the center of the lower rack, this will block the spray nozzle washing action when the lower rack is pushed in.
Larger items that shield smaller items from the washing action.
Observe to see if there is a nesting of the bowls or silverware so that the water cannot reach all surfaces.
The spray arms are blocked from turning, for example, tall items or an item that fell through the racks.
If an item blocks the detergent dispenser from opening, this will not allow the detergent to mix with the water.

Read the use and care manual for the proper instructions on how to load the dishes for proper cleaning.
Before closing the door and starting, manually spin all accessible spinning parts to ensure they can spin freely.
Most dishwashers have a spray arm inscribing a circle in a square box, so the corners don't get much water. Take care to keep the hardest to clean dishes like coffee cups out of the corners.

Improper filling of water in the tub. Water pressure must be between 15 and 120 pounds per square inch. After the fill has stopped, check the water level in the tub. On most models, it should be even with the heating element in the bottom of the dishwasher.