Diagnosing a dishwasher can be tricky.
The same malfunction can cause different symptoms.
In order to troubleshoot your dishwasher, you need to know how it is supposed to work. So you really need to know the cycles below, and the order in which they happen.
There are certain types of dishes that you should NOT wash in your dishwasher under any circumstances. For example, certain kinds of “darkening” in fine silverware is normal, and does not indicate a problem with your dishwasher. Other things to watch out for:
- Cutlery with wood, bone or horn handles may crack or break or split under high temperatures and/or hydraulic pressure.
- The high-pressure hot water jets may also be enough to wash the hand painting off your hand-painted china.
- Lacquerware, genuine antique milkglass, or anodized aluminum may discolor.
- Iron skillets or pans may rust. Any rust that comes off is also very abrasive and will not be good for the pump and seals.
- Antique or very delicate crystal or china can break easily under high temperatures and pressures.
Dishwasher Cycle Sequence
Cold water can kill your wash quality. It can also indicate a drain or air gap problem.
Before letting any hot water into the tub, we MUST make sure the tub has no cold water left in it from the last wash, or from the dishes when you load them.
Therefore, in most designs, a new wash cycle starts with the pump operating for a minute or so in the “drain” mode. This flushes out any cold water left in the tub.
An electric solenoid water fill valve then opens to let hot water into the tub. The water level in the tub is controlled by a flow-control washer built into the water valve…it compensates for variations in the water supply pressure. The timer controls how long the solenoid valve stays open.
Most designs use a float switch to prevent accidental overflow (flooding) during the fill cycle. It should be noted that it is NOT there to control the water level.
It is important that the water be as HOT as possible. A cold water fill can cause problems with your wash quality. Since the water heater in your home provides the water, it should be as close to the dishwasher as possible. If it is far away, the dishwasher fill with cold water from your house piping until the hot water reaches it.
The heater in the dishwasher tub can help, but it is really there to keep the water from cooling off too fast…not to heat it up in the first place. It also helps to dry the dishes at the end of the cycle.
The pump then starts in the “wash” mode. Water is channelled to the spray arms which spray the hot water at the dishes.
In some models, detergent is dispensed during the wash cycle.
The timer controls when this occurs. In most designs, the dispenser is opened either by a solenoid or by a bi-metallic trigger. GE uses a cam on the timer to trip open the dispenser.
At the end of the “wash” cycle, the pump enters the “drain” mode. The hot, soapy wash water is flushed out and drained.
The pump drains water from the tub in one of two ways. See the illustrations below.
In some “direct-reversing” designs, the motor reverses direction and a separate impeller pumps the water out.
In other designs, a solenoid-controlled valve opens to allow the pump to discharge to the drain line.
The timer controls the direction of the motor or the opening of the drain valve.
After the drain cycle, the tub fills again, with clean hot water.
Note that the dishwasher also operates in the “wash” mode during the “rinse” cycle. That is, it’s taking water from the bottom of the tub and spraying it at the dishes. The only significant difference is that it is clean, clear water; no detergent is being released during the “rinse” cycle.
However, some dishwashers DO open rinse agent dispensers; chemicals that help to diminish spotting when drying. The timer controls when this occurs. In most designs, the dispenser is opened either by a solenoid or by a bi-metallic trigger. In some machines, GE used a cam on the timer to trip open the dispenser.
After the final drain cycle, most models also have a “dry” cycle.
In some machines, the circular heater in the tub does this.
In others, a blower fan circulates air inside the cabinet to evacuate steam and dry the dishes somewhat.
Dishwasher designs can be broadly classified into horizontal-shaft and vertical-shaft designs. Horizontal shaft machines are affectionately known as “sidewinders.”
Some horizontal-shaft designs in this manual use a single-direction motor and a valve to divert the pump discharge to the drain. Some sidewinders are direct reversing.
Except for Kitchenaid, all vertical-shaft designs in this manual are direct-reversing. Most Kitchenaid machines use a single-direction motor and a solenoid drain valve; although the latest ones resemble Whirlpool machines and are direct-reversing.
Except for Maytag, all vertical-shaft designs in this manual have a combination pump and motor unit mounted in the bottom center of the tub. Late model Maytags have this, but in earlier Maytag machines, the motor is mounted off-center and drives the pump through a belt.
Dishwashers can be further classified into reversing and single-direction machines.
In reversing machines, the motor spins in one direction to wash or rinse the dishes, and it reverses to drain the tub.
Single-direction machines always spin in the same direction…when they need to drain, a solenoid activates a valve that diverts water flow to the drain.
Late model machines have separate wash pumps and drain pumps.