Rmc Module Plug Test (Electric Pto) - Craftsman 28906 Professional Shop Manual

ELECTRICAL SYSTEM
RMC module plug test (electric PTO)
1. Disconnect the molded 8-pin plug from the RMC
module. See Figure 7.5.
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Looking at the plug head-on, it will be configured
as shown in the diagram: There will be 8 female
pin terminals. When probed they should yield the
results described in the following sections.
See Figure 7.6.
Empty
Empty
Figure 7.6
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,
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Top left middle square-shape: Yellow wire with
Black trace:
Behavior: Should show DC power with the key
on.
Circuitry: The yellow wire with black leads to
the PTO switch and the PTO relay. It allow the
RMC module to apply a ground to the coil of the
PTO relay, which energizes the relay, severing
the ground to the PTO clutch. When the PTO
relay energizes it also applies a ground to the
PTO switch. This ground loops back to the PTO
relay's coil, latching it in the energized position.
Interpretation: If behavior is correct, the N.C.
side of the PTO switch/circuit is functioning
properly
If there is continuity to ground, then there is a
short to ground either between the PTO relay
and the RMC module or in the PTO switch circuit.
Bottom left middle rounded-shape: Yellow wire
Behavior: When the terminal is probed (yellow
wire), there should be continuity to ground only
when the seat is empty.
Circuitry: The yellow wire leads to the seat
safety switch, where it finds a path to ground
when the seat is empty.
Interpretation: If behavior is correct, the seat
safety circuit is good. If there is continuity to
ground when the seat is occupied, 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 seat is empty, the
switch may be inoperative or there may be an
open condition in the wire leading to it.
Top right middle square-shape: There is a red
wire with black trace between yellow wire with a
black trace and the green wire. This wire pro-
vides 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.
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 or a shorted reverse safety
switch.
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