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11.8 DIODES AND RECTIFIERS
Diodes are solid state, semiconductor devices. They
contain no moving parts and conduct current better in
one direction than the other. They are electrical "check
valves" and permit current flow in one direction, but not
in the other.
Diodes allow current to flow through one circuit without
"backing up" into another. In engine alternator circuits a
diode is used to convert current which flows back and
forth (AC) in a circuit to current which flows only in one
direction (DC). A device which converts alternating
current to a direct current is called a
RECTIFIER
. A
diode is one type of a rectifier.
To check a diode, isolate if from the circuit by
disconnecting one end. With a multitester set on the
lowest ohms scale setting, measure the resistance in
one direction, reverse the test leads, and measure in
the other direction. Readings should be high in one
direction and low in the other. (If the readings are low in
both directions, the diode is shorted, and if the
readings are high, the diode is open.) If the readings
are the same in both directions, the diode is defective
and must be replaced.
IMPORTANT:
Diodes are marked to indicate polarity (a
band on one end, an arrow on the side, or they fit on a
holder only one way.
Rectifiers
A battery is charged through the use of an alternator
located in or on the engine. A charging circuit contains
a rectifier because alternators produce alternating
current (AC) and batteries require direct current (DC)
for charging.
The rectifier may be built into the engine or it may be
an external part. It may also contain a regulator to
prevent overcharging the battery. (Servicing of
rectifiers built into the engine should be done by an
approved engine manufacturer’s service center. Such
a service center has access to the information and
parts required to test and repair or replace engine
components, including rectifiers and regulators.)
Units that contain both a rectifier and regulator are
tested in a working circuit to make sure the regulator
portion of the device is operating.
11.9 ELECTRIC CLUTCH
The electric clutch is used to turn on and off the
attachment used on the unit by use of a switch on the
dash panel. The clutch is also designed so that a brake
is applied to the output shaft when the clutch is
disengaged (off).
The field coil is mounted to a bearing support and does
not rotate. The rotor is attached to the power output
shaft and rotates around the field assembly. The
armature is attached to the output pulley. The armature
assembly is held close to the rotor by the brake
assembly. The clutch is engaged by applying current to
the coil connection. This results in a current flowing
through the coil, magnetizing the coil pulling the
armature onto the rotor with sufficient force to hold the
two pieces together, effectively connecting the output
and the input shafts together. Pulling armature against
the rotor pulls it away from the brake, releasing the
brake.
Engine Electrical Components
Engine servicing and repair should be referred to local
engine manufacturers service centers that have the
service information and parts available to properly
service the engine. Ariens dealers should be able to
test engines and engine components to pinpoint
troubles and narrow them down to properly advise the
engine serviceman.
11.10 ELECTRICAL
Initial check out: Make sure that all switches are in their
proper position for starting: (A) PTO off. (B) transaxle in
neutral position. (C) operator on the seat. (D) the
parking brake pedal pushed. (E) cruise control in the
off position. If no power to start the engine, start the
following check list:
Step 1:
Check out the battery. Use a hydrometer on all
the battery cells to see if one or more is bad. Also use a
voltmeter to check for proper voltage. Replace the
battery if necessary and/or charge to proper level.
Figure
52