Gravely Promaster 260Z, Руководство по обслуживанию

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Voltage Measurement
There are two basic rules to be remembered when
using a voltmeter. A voltmeter measures the voltage
difference between the test leads and the voltmeter is
always connected across the circuit under test.
Current Measurement
The two rules to remember when measuring current
with an ammeter are; an ammeter measures the cur-
rent that flows through the meter, and to measure cur-
rent an ammeter must be connected into the circuit.
The latter rule means that the circuit must be opened,
and the ammeter wired into it. Because this procedure
is usually difficult, an ammeter is seldom used for trou-
bleshooting.
Resistance Measurement
An Ohmmeter is used to make resistance measure-
ments and to check continuity through wires and elec-
trical components.
There is one rule to keep in mind when using an ohm-
meter. The ohmmeter has a self contained battery and
requires no electrical power. Using the ohmmeter on a
circuit that has power applied may result in damage to
the meter.
IMPORTANT: Disconnect the equipment battery when
making Ohmmeter test or damage to the Ohmmeter
may result.
IMPORTANT: An ohmmeter reads the resistance of
whatever component is connected between the test
leads. It can be used to check wires, coils, light bulbs,
or any item that conducts current.
SWITCHES
Switches either open a circuit to stop current flow or
close and allow current to flow through.
A normally open (N.O.) switch prevents current flow
until the switch is actuated, completing the circuit and
allowing current to flow through it. An example is a light
switch - the lights are off until the switch is actuated
and the lights go on.
A normally closed (N.C.) switch allows current to flow
until the switch is actuated, breaking the circuit and
stopping current flow through it. An example is an
ignition switch that grounds the magneto when in the
off position (completing the circuit) but opens the circuit
when in the ON position allowing the engine to operate.
Switches are selected with regard to Current rating
(contacts must be of sufficient size to carry the required
current), Voltage rating (switches insulated for specific
voltages), Case or housing (switches that are exposed
to moisture and must be sealed to prevent moisture
from entering), and Actuating type (push, pull, rotary,
momentary contact, or micro switches).
NOTE: Check that the connections to the switches are
secure and that a switch is being activated properly
before performing electrical test on switches. (Safety
switches on speed selector and clutch levers may be
out of adjustment and not activating.)
IMPORTANT: When checking switches, remove them
from their respective circuit by disconnecting the wires
from the switch at the connector(s). Damage could
result to the meter or machine components if switches
are left in.
Normally Open Switch
To test a normally open switch (key, headlight, safety,
or seat) connect the ohmmeter across the switch
terminals. Meter should indicate open circuit (infinite
resistance). Activate the switch. The ohmmeter should
read up scale to zero resistance (Close Circuit). This
indicates the switch is operating properly. Also check
from each terminal to the switch case (if case is metal).
reading should show infinite resistance indicating no
short to ground.
Variation from test results described indicates a
defective switch.
Normally Closed Switch
To test a normally closed switch connect the ohmmeter
across the switch terminals. Meter should indicate a
closed circuit (zero resistance). Activate the switch and
the meter should move to open circuit (infinite
resistance). Check from each terminal to ground
(switch case). Meter should show open circuit (infinite
resistance).
Variation from test results described indicates a
defective switch.
Ignition Switch
NOTE: Refer to the wiring diagram of the unit involved
to determine switch functions and test using the meth-
ods described.
The ignition switch incorporates a number of functions,
although not all functions are used on all equipment.
The switch has three positions: OFF, RUN, and a
momentary contact START position. Use an ohmmeter
to check the continuity of the switch in each position.
OFF Position - Should be continuity between contacts
G and M. These connections ground the engine
magneto and stop the engine in the OFF position.
RUN Position - Should be continuity between contacts
B and A. These connections supply power to the rest of
the wiring harness. Connections G and M open to each
other.
START Position - Hold switch in START position while
testing. There should be continuity between contacts
S1 and S2. These connections apply power to close
the solenoid contacts and operate the starter motor.
In addition to the above test, place the switch in the run
position and check between each contact and ground
(metal case) to be sure no terminals are grounded. If
the switch is operating properly, there will be no
continuity between contacts other that those described.