Filter
Top Products
Timers
A Timer OperatiOn
D. ELECTRICAl. CONTROLS
The timer is the central control point of the electrical components. All timers used on Kenmore Dishwashers are similar
in operation and design. The only difference is in complexity due to the variation in function and features of the various
models
MOTOR
CAM SWITCH
FIGURE54
All electromechanica! timers consists of two basic components; a motor, and cam switches, assembled into one unit..
(Figure 54). To fully understand the function and relationship of these two components to one another, it is necessary
to examine each component in more detail
Timer motors may vary slightly in appearance, but each functions in the same manner It is a synchronous-type motor,
similar to those used in electric clocks, with a small pinion which drives a cam through a gear arrangement.
The cam switches are enclosed in a case to protect them from damage and contamination by foreign particles which
may cause a malfunction The number of switch contacts and cams varies with the number of functions the dishwasher
performs
The particular shape of the cam varies with the number of switch contacts it controls and the length of time each
switch contact is ctosed_ Figure 55 shows a very simple cam that controls one switch contact, which is closed for
two increments of the timer cycle Let's assume that this cam is designed for a timer that has an advancement of
six deglees (6 °) every sixty seconds The cut-out portion of this cam, therefore, is twelve degrees, and the cam switch
contacts are closed for only two minutes during the complete cycle
CAM----/
CAM----.-/ t
FIGURE55
A single metal strip, called a cam follower, (Figure 55) is anchored to each cam switch arm and as the cam turns,
this metal Strip follows the contour of the outer circumference of the cam, thus causing the cam switch arm to make
and break contact at the proper time
In Figure 5B we see a more complicated cam, This cam was designed to control one or possibly two switch arms that
have dual contacts You will note that this cam has raised, cut-out, and neutral portions The raised portions
force the cam switch arm against the outer contact and the cut out portions allow the cam switch arm to make
contact with its inner contact. Both contacts are open when the cam follower is on the neutral section of the cam
SWITCH ARM
CONTACT
CAM . NEUTRAL
FOLLOWER SECTION
CAM _ CONTACT
INNER OUT
PORTION
-CAM
FOLLOWER
OUTER
CONTACT
€
FIGURE56
49