DISHWASHER Repair Manual MODEL

Dishwasher Sytem Basics - Chapter 1 - Dishwasher Repair Manual http://www.appliancerepair net/dishwasher-repair-1.html[3/25/2013 10:30:46 AM] shorter-lived than other major appliances. Why? Well, to answer that question, let's all be little deviants for a moment, and design ourselves a torture chamber—for an electric motor. What is absolutely the worst enemy of electricity in a machine? Water, right? Well, then, let's use the motor to pump water, and let's mount the motor right underneath the water seal. That way if the seal leaks at all, lots of hot, steamy water will run right down on top of the motor and rust it up and short it out. While we're at it, let's run some bits of broken glass and big chunks of food and nutshells and seeds through the pump, so we can chew up the seals and the impeller and also to introduce some nice, sudden deceleration shocks to the motor and pump. And of course, for maximum heat buildup, let's mount the whole motor and pump package in a tiny, cramped, steamy, dusty, poorly ventilated space, right beneath a tub full of hot steamy water. Get the picture? 1-2(a) CYCLES STARTING DRAIN CYCLE Cold water can kill your wash quality. (see Chapter 3) So 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. Therefore, in most designs, a new wash cycle starts with the pump operating for a minute or so in the "drain" mode. FILL CYCLE An electric solenoid fill valve then opens to let hot water into the tub. The timer controls how long the solenoid valve stays open, which controls the water level. A flow-control washer built into the valve compensates for variations in the water supply pressure. Most designs use an anti-flood float switch to prevent accidental overflow during the fill cycle. WASH 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. WATER HEATING Most designs also have a water heater in the tub to maintain proper water temperature during the wash cycle. In some designs, the heater also dries the dishes at the end of the wash. RINSE CYCLE Note that the dishwasher also operates in the "wash" mode during the

Dishwasher Sytem Basics - Chapter 1 - Dishwasher Repair Manual http://www.appliancerepair net/dishwasher-repair-1.html[3/25/2013 10:30:46 AM] "rinse" cycle. The only substantial difference is that no detergent is being released during the "rinse" cycle. 2nd or 3rd DRAIN CYCLE At the end of the "wash" and "rinse" cycles, the pump enters the "drain" mode. The pump drains water from the tub in one of two ways. In some "direct-reversing" designs, the motor reverses direction and a separate impeller pumps the water out. (Figure 1-A) In other designs, a solenoid-controlled valve opens to allow the pump to discharge to the drain line. (Figure 1-B) The timer controls the direction of the motor or the opening of the drain valve. DRY CYCLE Most models also have a "dry" cycle. In some machines, the heater does this. In others, a blower fan circulates air inside the cabinet to evacuate steam and dry the dishes somewhat. Figure 1-A: Typical Direct-Reversing Design Figure 1-B: Typical Single-Direction Machine

DISHWASHER Repair Manual MODEL

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