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ELECTRICAL SYSTEM
•
Circuitry: The yellow wire with black trace leads
to the PTO switch, where it finds a path to
ground when the PTO is ON.
•
Interpretation: If behavior is correct, the N.C.
side of the PTO switch /circuit is functioning
properly
If there is continuity to ground when the PTO is
OFF, the switch may be inoperative or there may
be a short to ground in the wire leading to it.
If there is not continuity to ground when the PTO
switch is ON, the PTO switch may be inopera-
tive, or there may be an open condition in the
wire that leads to it.
E There is a red wire with black trace between
yellow wire with a black trace and the green
wire. This wire provides the module with
input from the reverse switch.
•
Behavior: When the tractor is in reverse, this
terminal should have continuity to ground.
•
Circuitry: This wire runs directly to the reverse
safety switch on the drive pedal shaft. This is a
simple metal tang switch that grounds-out
against a bolt.
•
Interpretation: Continuity to ground when the
tractor is not in reverse would indicate a short to
ground. This could take the form of a chafed wire
contacting ground, a bent reverse safety switch
that is always in contact with another metal part,
or a broken plastic insulator that separates the
switch from the drive pedal shaft.
Lack of continuity to ground would indicate a bro-
ken or disconnected wire leading to the reverse
safety switch, or a switch that is not closing
because of physical damage or corrosion.
F At the opposite end of the top row from the
yellow wire with black trace is a green wire.
•
Behavior: The green wire should always have
continuity to ground.
•
Circuitry: The green wire leads to ground.
•
Interpretation: If this ground path is not good,
there will probably be other ground-related
issues with the tractor: slow starter motor, slow
battery charge, dim lights. All ground connec-
tions should be mechanically secure and corro-
sion free.
G The red wire on the OCR plug carries bat-
tery voltage.
•
Behavior: D.C. battery voltage should show up
on a volt meter when the red probe is touched to
this terminal and the black probe is grounded,
regardless of the key switch position.
•
Circuitry: This wire draws power directly from
the B terminal on the key switch.
•
Interpretation: If there is no battery voltage at
this terminal, the tractor is probably not function-
ing at all. Look for a blown fuse, disconnected
battery, disconnected ammeter or some other
major fault.
H The purple wire provides a ground signal
to the RMC module when the key switch is
placed in the REVERSE CAUTION MODE.
•
Behavior: There should be continuity to ground
at this terminal when the key switch is in the
REVERSE CAUTION MODE position.
•
Circuitry: When the key switch is in the
REVERSE CAUTION MODE position, a ground
path is established by connecting terminal A2 to
terminal L within the key switch. The purple wire
from the RMC module connects to A2, and a
green ground wire connects to L.
•
Interpretation: If the purple wire fails to reach a
ground path when the key switch is in the
REVERSE CAUTION MODE position, the RMC
module will not arm or operate. Check the key
switch for continuity between A2 and L in the
REVERSE CAUTION MODE position, confirm
that the green wire connecting to the L terminal
does have good continuity to ground, and check
for any loss of continuity in the purple wire that
extends from the key switch to the RMC module,
including the molded connector between the two
components.
I If the RMC plug test indicates fault with any
of the safety switches, the next step is to test
the suspect switch. The operation of those
switches is described in the following sec-
tions.
3.
Understanding the PTO switch
3a. A-COM is in the starter inhibit circuit. It is a
normally closed (NC) set of contacts. When
the PTO is OFF, and the contacts are
closed, power coming from the brake switch
(key switch in START, brakes ON) through
the orange wire with black trace is passed
on to the trigger terminal on the starter sole-
noid through the orange wire with white
trace.
116
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