Dishwasher gets sediment on dishes

SOURCE: Dishwasher leaves a fine black sludge

I work in a hospital and have seen this problem with our scope washers (a very sophisticated dishwasher with lots of safety features) and it turned out to be a faulty pump motor.  Some pumps have black ceramic magnet in them and if it cracks it will breakdown and mix in with wash water creating a black smudge on everything with bits. Just as you described.  Unfortunately, I have never taken a part a dishwasher motor so I don't know if it's the same type of motor. 

SOURCE: Maytag Quiet Servies 100

make sure your getting at least 120 degrees in water.Check the heater element,rinse aid ,clogged up spray arms.These are the most common and need to be 100% ok.

SOURCE: Dishes not being rinsed thoroughly in our GE Nautilis Dishwasher

If your dishwasher is cleaning poorly, check these:
Water-inlet valve Most cleaning problems are caused by the dishwasher not getting enough wash water, so the water-inlet valve is often to blame. This valve is usually at the bottom left or right of the dishwasher, behind the lower access panel. It's the device with the main water line from the house, a rubber tube to the dishwasher, and two wires attached to it. 

When a water-inlet valve is defective, you may hear the sound that's usually referred to as "water hammer." If the water-inlet valve is defective, you need to completely replace it. 

Dishwasher Water Inlet Valve Replacement

Be sure to read and understand any instructions that come with the new water inlet valve.

Tools required: 

Adjustable wrench

Multi-Screwdriver 

Pliers 

Step 1. Disconnect the dishwasher from its power source. 

Note: Dishwashers are usually wired directly to the home’s electrical system. To disconnect the power, switch off the circuit breaker or remove the fuse for the electrical circuit the dishwasher is attached to. Try to turn the unit on after disconnecting the power to be sure you were successful. 

CAUTION: If you’re not sure you’ve shut off the power properly, DO NOT CONTINUE. Call a qualified appliance repair technician to complete the repair. 

Step 2. Turn off the water supply to the dishwasher. This is usually underneath the kitchen sink or in the basement or crawlspace near the location of the dishwasher. Pliers may be helpful here. 

Note: If there are no shut-off valves, you must shut the water off at the main water supply valve for your home. 

Step 3. Remove the lower panel(s) of the dishwasher. These are usually held by 2 to 4 screws at the upper and lower corners of the panel(s). 

The inlet valve is usually near the front of the dishwasher. Attached to the valve you’ll see: 2 or 4 wires, the water supply line from the house and the water feed line that goes to the dishwasher. 

Step 4. Remove the household water supply line from the valve. The line is usually secured with a brass compression nut. The water supply line is usually copper or braided stainless steel. 

CAUTION: Water supply line may be hot. 

Step 5. Remove the fitting from the valve the water supply line was attached to. This fitting may be very difficult to remove. It may help to put the valve into a vice in order to remove the fitting. If you cannot remove it, replace it. The fitting is not an appliance part but a plumbing part that is available at most hardware stores.

Step 6. Remove the screws holding the valve to the dishwasher frame. 

Step 7. Label the wires to the valve so you’ll be sure to reattach them correctly. 

Step 8. Remove the wires from the valve. 

Step 9. Remove the clamp on the black rubber water discharge tube and pull the tube off of the valve. 

Step 10. Reinstall the old fitting (or a replacement fitting if necessary) onto the new valve the water supply line was attached to. Use Teflon tape or pipe joint compound as a thread sealant. Make this fitting tight to prevent leaks. Make sure that the fitting points in the same direction as the old one so that the water supply line will meet up with it properly. 

Step 11. Install the new valve in the reverse order of the removal instructions. 

Note: The water supply line is under high pressure. Be sure to tighten the fittings properly. 

Step 12. Turn on the water to the machine, and check for and correct any leaks. 

Step 13. Reinstall the access panel(s). Restore the power to the dishwasher and test. 

Note: You may have to let the dishwasher run a few minutes before it reaches the next water fill cycle. 

Internal filters Every dishwasher has some type of filter to keep large food particles and foreign objects away from the pump assembly:

• Most modern dishwashers have self-cleaning filters that don't need any routine cleaning.



• Some have filters in the bottom of the dishwasher that you need to periodically clean. You don't need any tools to remove the filter, and cleaning it is easy. Consult your owner's manual to determine which type you have and its maintenance requirements.

If your filter is clogged, it may be causing the cleaning problem. 

Drain valve Some dishwashers have a valve (or gate) that should open only during draining. If debris lodges in the valve, it can't close properly, so water drains out during the wash cycle. Most dishwashers drain into the garbage disposer. If yours does that, listen for water flowing into the disposer during the wash cycle. If you can hear it then, the drain valve may be clogged.

Spray arms There's a spray arm at the bottom of your dishwasher--it may have a tall spray tube mounted to the center of it. There may also be a spray arm located directly beneath the upper rack of dishes and/or above the upper rack.

If debris is blocking the holes in the spray arms where the water comes out, it could cause cleaning problems. Regularly inspect each of the spray arms and clean out the holes as necessary. 

Water temperature To get the best cleaning results, the water entering your dishwasher needs to be hot enough. Try running the hot water in your kitchen sink for about 30 seconds before starting the dishwasher, to pre-heat it. Also, if your dishwasher lets you select a higher wash or rinse temperature, try that to see if it helps. 

To check the temperature of the hot water that comes from your kitchen faucet use a waterproof thermometer. If the water isn't 120 degrees Fahrenheit, your dishwasher may have trouble getting your dishes clean. You could increase the temperature of the hot water to the whole house--and therefore the dishwasher--by adjusting the hot water heater thermostat.

Warning! To lessen the risk of scalding, don't set the hot water heater temperature higher than 120 degrees Fahrenheit. 

Detergent cup Dishwashers don't perform their best if detergent is introduced only at the beginning of a cycle, so add detergent to both parts of the cup. 

SOURCE: soap build up on dishwasher. Dries white and stays on dishes.

the spray arms is eather bad or the wash motor ,,,,, it isn't spraying water onto the dishes with any force.
Larry

SOURCE: Sand (?) on dishes

Buy a box of brand name dishwasher detergent powder. Stop using generic, ultra-cheap soaps, they are filled with "filler" minerals that accumulate in the dishwasher and build up in the plates and silverware.
Good Luck!