If the pump does not spray out a
steady stream of fluid, the problem
is in the pump circuit. It should be
tested in the same way as any
other electrical circuit. Make sure it
gets power from the switch when it
should, then check the ground. If
the power to the pump is good and
there is a good ground, the
problem is the pump. Pumps are
not rebuilt or repaired; they must
be replaced.
11.6.3 Power Windows
A power window uses a control
switch, reversible electric motor,
circuit breaker, fuse, and related
wiring to operate the door
windows.
A small electric power window
motor is located inside each door
to operate the window regulator
(up-down mechanism for the
glass). The motors have a
Figure 6-64 - Schematic simple power
window circuit for a passenger-side window.
gearbox, or transmission (usually worm and ring gear), that changes the rotating motion
of the motor armature into a partial rotation of a larger gear. This action pushes the
window open or closed.
A circuit breaker protects the window motor from overheating damage. The breaker can
open if the switch is held in one position too long. The circuit breaker can be located
inside the motor or elsewhere in the circuit. A simple power window circuit for a
passenger-side power window is shown in
Figure 6-64
.
Some power windows will stop or reverse direction if an obstruction resists window
closing. In some of these systems, a magnetic trigger wheel is mounted on the motor's
armature shaft. As the trigger wheel turns, it creates a signal in a magnetic or Hall-effect
sensor in the motor assembly. If the sensor outputs a slower-than-normal signal, the
power windows ECM will cut voltage or reverse polarity of the voltage going to the
window motor. This stops the window or lowers it to prevent damage to objects or injury
to people who accidentally put their hands, head, or arms into the path of the window as
it closes.
Power window service.
When none of the power windows work, you first check the
fuse or circuit breaker for the whole system. If only one of the windows is inoperative,
use a test light to check for power to its switches.
If you hear a humming sound when a window switch is pressed, the motor gearbox may
have stripped gear teeth. The plastic gears in the window motor gearbox can strip after
prolonged service. The motor will spin, but movement will not be transferred to the
window. If the motor or the switches are found to be bad, they should be replaced.
With hard-to-find problems, refer to the service manual wiring diagram for the power
windows, which will show all the components that could affect power window operation
and help with troubleshooting.
NAVEDTRA 14050A
6-63
