Craftsman 28906 Professional Shop Manual

Craftsman 28906 Professional Shop Manual

Electric module


Shop Manual
Electric Module
NOTE: These materials are for use by trained technicians who are experienced in the service and repair of outdoor power
equipment of the kind described in this publication, and are not intended for use by untrained or inexperienced individuals.
These materials are intended to provide supplemental information to assist the trained technician. Untrained or inexperi-
enced individuals should seek the assistance of an experienced and trained professional. Read, understand, and follow all
instructions and use common sense when working on power equipment. This includes the contents of the product's Oper-
ators Manual, supplied with the equipment. No liability can be accepted for any inaccuracies or omission in this publication,
although care has been taken to make it as complete and accurate as possible at the time of publication. However, due to
the variety of outdoor power equipment and continuing product changes that occur over time, updates will be made to these
instructions from time to time. Therefore, it may be necessary to obtain the latest materials before servicing or repairing a
product. The company reserves the right to make changes at any time to this publication without prior notice and without
incurring an obligation to make such changes to previously published versions. Instructions, photographs and illustrations
used in this publication are for reference use only and may not depict actual model and component parts.
© Copyright 2010 MTD Products Inc. All Rights Reserved
MTD Products Inc. - Product
Training and Education
,FORM NUMBER-769-06468


Table of Contents

Summary of Contents for Craftsman 28906

  • Page 1 Professional Shop Manual Electric Module 28906,28980, 28981,28984 NOTE: These materials are for use by trained technicians who are experienced in the service and repair of outdoor power equipment of the kind described in this publication, and are not intended for use by untrained or inexperienced individuals. These materials are intended to provide supplemental information to assist the trained technician.
  • Page 2: Table Of Contents

    Table of Contents Introduction ....................... Professional Shop manual intent ..............Fasteners ......................Assembly ......................Description of the GT series ................Model and Serial Numbers ................Precautions ...................... RMC Module ....................Key switch ......................RMC module ....................RMC module plug test (electric PTO) ...............
  • Page 3 CRAFTSMAN...
  • Page 4: Introduction

    ELECTRICAL SYSTEM INTRODUCTION INTRODUCTION • Bullet points: indicate sub-steps or points. This module is divided into four sections: Disclaimer: This Professional Shop Manual is intended for use by trained, professional technicians. Section 1: About this module and precautions • Common sense in operation and safety is Section 2: Components assumed.
  • Page 5: Description Of The Gt Series

    CRAFTSMAN The model number is 13AR91PP099 The break down Description of the GT series of what the number mean is as follows: This tractor platform introduced in the 2010 season.. 13 ......lawn tractor See Figure 1.1..A....... sales level ..
  • Page 6: Rmc Module

    ELECTRICAL SYSTEM ELECTRICAL SYSTEM COMPONENTS Key switch RMC Module The Key Switch is similar to those used in a variety of MTD applications since 1999. The difference in this The RMC module contains electronic logic circuits. case is that it is incorporated in the same housing as When diagnosing anything that is connected to the the RMC module;...
  • Page 7 CRAFTSMAN M is connected to the magneto by a yellow wire, Symptom-No crank and no starter solenoid G is connected to ground by a green wire, and click: Power is not getting to the trigger spade on A1 is connected to the after fire solenoid.
  • Page 8: Rmc Module

    ELECTRICAL SYSTEM RMC module Symptom-After fire solenoid does not work: enqine starts and dies: The after fire solenoid is The RMC Module is in the same housing as the key powered directly by the red wire from the B ter- switch, and is not available separately.
  • Page 9 CRAFTSMAN When the RMC module is armed and turned- To re-arm and turn the module ON: on: The tractor will operate identically to when If the key is in REVERSE CAUTION MODE the module is disarmed, except that the operator...
  • Page 10: Rmc Module Plug Test (Electric Pto)

    ELECTRICAL SYSTEM RMC module plug test (electric PTO) Top left middle square-shape: Yellow wire with Black trace: Disconnect the molded 8-pin plug from the RMC module. See Figure 7.5. Behavior: Should show DC power with the key Circuitry: The yellow wire with black leads to the PTO switch and the PTO relay.
  • Page 11 CRAFTSMAN Lack of continuity to ground would indicate: Interpretation: If the purple wire fails to reach a ground path when the key switch is in the • A broken or disconnected wire leading to REVERSE CAUTION MODE position, the RMC the reverse safety switch module will not arm or operate.
  • Page 12: Rmcmoduleplug Test(Manualpto)

    ELECTRICAL SYSTEM RMCmoduleplug test(manualPTO) Top left rounded-shape: Yellow wire Disconnect the molded 8-pin plug from the RMC Behavior: When the terminal is probed (yellow module. See Figure 7.7. wire), there should be continuity to ground 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.
  • Page 13 CRAFTSMAN Interpretation: If this ground path is not good, Circuitry: When the key switch is in the there will probably be other ground-related REVERSE CAUTION MODE position, a ground issues with the tractor: slow starter motor, slow path is established by connecting terminal A2 to battery charge, dim lights.
  • Page 14: Electric Pto Switch

    ELECTRICAL SYSTEM Electric PTO switch PTO relay Understanding the electric PTO switch The PTO relay is located on the main harness, under- neath the electric PTO switch. See Figure 7.10. In A-Com, power is supplied to the PTO switch from the A1 terminal of the ignition switch through a red wire.
  • Page 15: Pto Switch (Manual Pto)

    CRAFTSMAN PTO switch (manual PTO) Brake switch (manual PTO) • The manual PTO switch is mounted on the right • The brake switch is mounted on the top side of side of the seat box section of the frame. the frame, on the left side behind the dash.
  • Page 16: Brake Switch (Electric Pto)

    ELECTRICAL SYSTEM To access the brake switch: Brake switch (electric PTO) Remove the deck by following the steps The brake switch is mounted on the top side of the frame, on the left side behind the dash. described in Chapter 8: Cutting Decks and Lift Shaft.
  • Page 17: Park Brake Switch

    CRAFTSMAN Park brake switch Reverse Safety Switch The park brake switch is only used on tractors that are The Reverse Safety Switch is a simple metal contact equipped with a manual PTO. The park brake switch is tang switch. a simple NO single pole single throw (SPST) switch.
  • Page 18: Seat Safety Switch

    ELECTRICAL SYSTEM Hyrdostatic transmissions Seat Safety Switch Tractors equipped with a hydrostatic transmission have The Seat Safety Switch is a double pole single throw the reverse switch mounted on the transmission, next (DPST) switch. Both poles are normally closed and it is to the selector plate.
  • Page 19: Starter Solenoid

    CRAFTSMAN Starter solenoid Lighting circuit The starter solenoid is mounted inside the seat box The lighting circuit is hot whenever the engine is run- section of the frame. See Figure 7.21. ning. It receives it's power from the A1 terminal of the key switch.
  • Page 20: Fuse

    ELECTRICAL SYSTEM Fuse ELECTRICAL DIAGNOSIS The 20A fuse is located inside the seat box section of NOTE: Electrical diagnostic procedures and the frame, on the left side near the deck lift shaft. tools are the same for all Cub Cadet and MTD See Figure 7.24.
  • Page 21 CRAFTSMAN Electronics Heat and Vibration: Heat and vibration are hard on most mechanical devices. The same is The outdoor power equipment has historically had rela- true of electronics. tively simple electro-mechanical controls. Customer expectations and regulatory demands continue to drive...
  • Page 22: Electrical Environment: Ac Vs. Dc

    ELECTRICAL SYSTEM Electrical environment: AC Vs. DC Ohm's Law: relates voltage, amperage, and resistance Most modern outdoor power equipment that has an electrical system complex enough to require diagnosis Ohm's law states that voltage is the product of resistance times current. will be equipped with an alternator that produces alter- nating current (AC).
  • Page 23 CRAFTSMAN Kirchhoff's current law: Kirchhoff's voltage law: Kirchhoff's current law deals with nodes. Nodes Kirchhoff's voltage law deals with voltage drops. are the junction of two or more wires or the junc- A voltage drop is the amount of voltage used up tion of a wire to a component.
  • Page 24: Types Of Circuits

    ELECTRICAL SYSTEM How the system is wired together Types of circuits The Rules: All circuits have some basic rules that There are three ways a circuit can be wired: must be followed: • Series All circuits must have at least one voltage •...
  • Page 25: Series/Parallel

    CRAFTSMAN Series/parallel Increased resistance • Series/parallel circuits have some sections wired Increased resistance is, as the name implies, an increase in resistance. in series and some in parallel. See Figure 7.30. Causes: This can be caused by loose or cor- roded connections, or connections that are insu- lated by grease, paint, or coatings.
  • Page 26: Digitalmulti-Meter

    ELECTRICAL SYSTEM DigitalMulti-meter Amperage: Most DMMs have a very limited capacity to test amperage (2-3 Amperes). When measuring cur- A DMM is the most useful tool to trouble-shoot rent flow, the meter must be connected in series with any electrical system. There is an amazing vari- the component to be measured.
  • Page 27: Wiringdiagramor Schematic

    CRAFTSMAN Wiringdiagramor schematic Some high impedance test lights are capable of indicating whether the current being sampled is A wiring or a schematic diagram, and the ability AC or DC. to read it are very important in troubleshooting circuit. The diagram shows how the circuit was...
  • Page 28 ELECTRICAL SYSTEM There are two primary reasons to measure Kohler makes a proprietary Rectifier/Regulator amperage: tester (Kohler Part Number 25 761 20 and the up-dated version: 25 761 20-S). This tester To check the out-put of a charging system works on Kohler regulator / rectifiers and the or battery.
  • Page 29 CRAFTSMAN Testingthe chargingsystem Check the stator for resistance across the AC leads. The resistance should fall Quick and dirty test: check voltage across the battery between the valves specified by the engine posts using a DMM set to read D.C. voltage with the manufacturer.
  • Page 30: Batteries

    ELECTRICAL SYSTEM Batteries Interpretation: If the ohm meter indicates no continuity between the two stator leads, Precautions: See Figure 7.39. there is a fault in the stator windings. If the ohm meter indicates continuity between CAUTION: Batteries produce flammable and either stator lead and ground, the stator explosive gases, particularly during charging: windings are shorted to ground.
  • Page 31 CRAFTSMAN Some charging systems do not work if the sys- Checking battery condition: There are three tem voltage falls below 6V. It takes a certain things to do when testing a battery: amount of voltage to excite the fields in the alter- •...
  • Page 32: Battery Testers

    ELECTRICAL SYSTEM Give the battery at least ten minutes for the Battery Testers: electrolyte to stabilize after charging the There are two major ways to check a battery's opera- battery or adding water to the cells. tion : Measure the temperature of the electrolyte Load test that checks the out-put of the battery in the middle cells of the battery.
  • Page 33 CRAFTSMAN Fixed load testing NOTE: C CA stands for cold cranking amps. The Fixed load testers (sometimes called toasters) are rating should be on the battery for aftermarket inexpensive load testers found at any auto parts store. batteries. For OEM batteries, contact the manu- See Figure 7.42.
  • Page 34 ELECTRICAL SYSTEM Capacitance testing Battery discharge test There are several brands of capacitance battery testers Occasionally a battery will discharge while sitting presently on the market. Capacitance battery testers unused. To test for a battery that is "leaking" voltage: use the battery being tested as their power source. Confirm that operator technique is not cre- These testers send a small AC signal through the bat- ating a situation that causes a draw.
  • Page 35 CRAFTSMAN If the battery is being checked indepen- Take a methodical approach to finding the dently of the equipment it powers, mea- problem. As a rule of thumb, start at one end of the circuit and work to the other.
  • Page 36: Voltage Drop Test

    ELECTRICAL SYSTEM Starting with a fully charged battery and bat- Voltage Drop Test tery cable connections that are clean and To review: tight, measure the battery voltage. See Figure 7.46. Ohm's law states that it takes voltage to push cur- rent through a resistance.
  • Page 37 CRAFTSMAN The voltage that shows-up on the meter is the With the starter engaged, this machine exhibited voltage that is being used to pass current a voltage-drop reading of 0.312 volts, indicating through a resistance in the circuit. a poor ground connection.
  • Page 38: Testing Switches

    ELECTRICAL SYSTEM Voltage drop on a good circuit should be less Testing switches than 0.1 volts. A voltage drop reading on the • Refer to the "Components" section of this chap- meter of greater than 0.2 volts indicates a fairly ter that describes the function of the individual substantial problem that demands attention.
  • Page 39: Relay

    CRAFTSMAN The male spade terminals that are associated Relay with each-other face each-other broad-surface Most of the relays used by MTD or Cub Cadet have to broad surface. See Figure 7.52. five pins. See Figure 7.53. Normally Closed switch element: Spades marked: "NC"...
  • Page 40: Diodes

    ELECTRICAL SYSTEM Diodes To test a relay: Test for continuity between the common and the What is a diode? A diode acts like a one way valve, NC terminals using a DMM. allowing current to flow in only one direction. See Figure 7.54.
  • Page 41 CRAFTSMAN Attach the negative lead of the DVOM to the side of the diode with a band on it. Place the positive lead on the other side of the diode. There should be continuity. See Figure 7.56. Continuity Silver band Figure 7.56...
  • Page 42: Schematics

    ELECTRICAL SYSTEM SCHEMATICS =.__== ---_,, ;_=_- © °m...
  • Page 43 CRAFTSMAN 021U UI:I O]lU ul:) .i.xl J._l/'13_ W!:3 "13 © !° i_!E ',Ill- vl "t3o INOA...

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