Gravely 989003, Service Manual

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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.
10.9 ENGINE ELECTRICAL COMPONENT
CHECK OUT
Engine servicing and repair should be referred to local
engine manufactures service centers that have the
service information and parts available to properly
service the engine. Gravely dealers should be able to
test engines and engine components to pinpoint
troubles and narrow them down to properly advise the
engine serviceman.
Ignition Switch
Check Procedure
1. Unplug the ignition switch and remove it from the
instrument panel.
2. Set a VOM in the ohm (Rx1) position. Connect one
lead to the "B" pin.
3. Turn the ignition key to the "off" position.
Sequentially touch pins R, I, A, S and the case with
the free meter lead. No circuit (infinity) should be
indicated.
4. Turn the key to the "Start" position and hold.
Sequentially touch pins S, R, I, and A with the free
meter lead. A circuit (.1 to .3 ohms) should be
indicated. Touch the free lead to the case. No
circuit (infinity) should be indicated.
5. Turn the key to the "Run" position. Sequentially
touch pins R, I, and A with the free meter lead. A
circuit (.1 to .3 ohms) should be indicated. Touch
the free lead to the case. No circuit (infinity) should
be indicated.
6. Replace the ignition switch if it fails any of the
above steps.
Relay
1. Turn the key to the "Run" position. Listen for the
relay to click. If the relay clicks it is most likely okay.
2. If the relay does not click, turn the key to the "Run"
or "Off" position. Use a VOM set to "Ohms" (Rx1)
position and verify continuity to ground at terminal
"85". If continuity to ground exists go on to step #4.
If not, make sure that all the interlock switches on
the path to ground are functional and activated in
the correct position.
3. Once continuity to ground is achieved, set the
VOM to the "12" volts D.C. position. Turn the key to
the "Run" position and check the voltage at
terminal "86". Turn the key to the "Off" position. If
voltage exists replace the bad relay.
4. Check the "Ohms" between terminals "86" and
"85" it should read between "87" and "105" Ohms.
Check the "Ohms" between terminals "30" and
"87A" it should read no circuit (infinity should be
indicated). Energize the relay and check the
"Ohms" between terminals "30" and "87" it should
read "Closed" (.1 Ohms). Terminals "86" and "85"
should read "Open" (infinite).
Time Delay
1. Turn the key to the "Run" position, check the
resistance (Ohms) between the "green" wire and
"brown" wire. With the seat switch open it should
read "Open" (Infinite).
2. Turn the key to the "Run" position, check the
resistance (Ohms) between the "green" wire and
"brown" wire. With the seat switch closed it should
read "Closed" (.1 Ohms).