Craftsman 28906 Professional Shop Manual page 13

CRAFTSMAN
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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.
Bottom left square-shape: The red wire on the
OCR plug carries battery voltage.
Behavior: With key switch in any of the run posi-
tions, 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.
Circuitry: This wire draws power from the A1
terminal on the key switch.
Interpretation: If there is not battery voltage at
this terminal, the tractor is probably not func-
tional at all. Look for a blown fuse or a bad key
switch.
Bottom left middle square-shape: There is a
black wire with a white trace between the red
wire and the white wire. This wire provides the
module with input from the park brake switch.
Behavior: When the brake pedal is depressed
and the park brake is set, a ground path is estab-
lished through the black wire with a white trace..
Circuitry: This wire runs to the brake switch,
then on to the park brake switch..
Interpretation: Continuity to ground when the
park brake is not set would indicate a short to
ground. This could take the form of a chafed wire
contacting ground or a shorted reverse safety
switch.
Lack of continuity to ground would indicate:
• A broken or disconnected wire leading to
the brake or park brake switches
• A switch that is not closing because of
physical damage or corrosion.
• Loss of ground to the park brake switch.
Bottom right middle rounded-shape: The white
wire provides a ground signal to the RMC mod-
ule 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.
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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 white wire
from the RMC module connects to A2, and a
green ground wire connects to L.
Interpretation: If the white 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 white wire that
extends from the key switch to the RMC module,
including the molded connector between the two
components.
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 sections.
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