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.
Table of Contents Introduction ....................................................................................................... 1 Professional Shop manual intent ...................................................................... Fasteners ......................................................................................................... 1 1 Assembly .......................................................................................................... Description of the GT series ..
CRAFTSMAN
ELECTRICAL SYSTEM INTRODUCTION INTRODUCTION • 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 Section 2: Components This section will describe the location and operation of the electrical components on the tractor. Where appropriate, some disassembly or component removal instructions will be included.
CRAFTSMAN Description of the GT series This tractor platform introduced in the 2010 season.. See Figure 1.1. The model number is 13AR91PP099 The break down of what the number mean is as follows: 13 ......................... lawn tractor ...A....................... sales level ...... R..................... engine code ........ 9 ................... tractor series .......... 1................ drive system ............ R ............. hood style ............... P........... deck ................... 099 ....
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 case is that it is incorporated in the same housing as the RMC module; the two items are not available separately. See Figure 7.1. The RMC module contains electronic logic circuits.
CRAFTSMAN M is connected to the magneto by a yellow wire, G is connected to ground by a green wire, and A1 is connected to the after fire solenoid. Symptom-No crank and no starter solenoid click: Power is not getting to the trigger spade on the starter solenoid. Test for proper battery voltage. Then check for power where the fused red wire with white trace connects to the B terminal. Check for continuity between B and S terminals in START position.
ELECTRICAL Symptom-After fire solenoid does not work: enqine starts and dies: The after fire solenoid is powered directly by the red wire from the B terminal of the key switch, and should operate independently of anything else on the tractor once the engine is running. If the alternator fails and battery power is not reaching the after fire solenoid through the key switch, it will not work. This is an unusual set of circumstances.
CRAFTSMAN When the RMC module is armed and turnedon: The tractor will operate identically to when the module is disarmed, except that the operator will be able to put the transmission in reverse with the PTO engaged and the cutting deck will continue to run The operator may put the tractor into and out of reverse as many times as they wish without having to re-arm or turn-on the module again.
ELECTRICAL RMC module plug test (electric PTO) 1. , Disconnect the molded 8-pin plug from the RMC module. See Figure 7.5. SYSTEM 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.
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 REVERSE CAUTION MODE position, the RMC module will not arm or operate.
ELECTRICAL SYSTEM RMCmoduleplug test(manualPTO) 1. , Disconnect the molded 8-pin plug from the RMC module. See Figure 7.7. Top left rounded-shape: Yellow wire Behavior: When the terminal is probed (yellow 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. NOTE: The yellow wire also branches off to the PTO switch.
CRAFTSMAN , 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 connections should be mechanically secure and corrosion free. 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.
ELECTRICAL SYSTEM Electric PTO switch PTO relay Understanding the electric PTO switch The PTO relay is located on the main harness, underneath 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. when the PTO switch is turned on this completes the circuit to allow power to go to the PTO clutch. It is a normally opened (NO) set of contacts. B-COM is in the safety shut-down circuit.
CRAFTSMAN PTO switch (manual PTO) Brake switch (manual PTO) • • The manual PTO switch is mounted on the right side of the seat box section of the frame. See Figure 7.11. The brake switch is mounted on the top side of the frame, on the left side behind the dash. The brake switch used on manual PTO tractors is a triple pole single throw switch. It has one set of contacts that are normally closed (NC) and the other two sets are normally open (NO). See Figure 7.12. A- NC PoleB- NO PoleC- NO Figure 7.
ELECTRICAL To access the brake switch: , , Remove the deck by following the steps described in Chapter 8: Cutting Decks and Lift Shaft. Brake switch (electric PTO) The brake switch is mounted on the top side of the frame, on the left side behind the dash. See Figure 7.15. Squeeze the tab on the underside of the brake switch with a pair of pliers, while pushing up on the brake switch. See Figure 7.13. Figure 7.13 , SYSTEM Reach in between the left side of the engine and the dash.
CRAFTSMAN Park brake switch Reverse Safety Switch The park brake switch is only used on tractors that are equipped with a manual PTO. The park brake switch is a simple NO single pole single throw (SPST) switch. The Reverse Safety Switch is a simple metal contact tang switch. The park brake switch is located on the frame, behind the dash on the right hand side. See Figure 7.16.
ELECTRICAL SYSTEM Hyrdostatic transmissions Seat Safety Switch Tractors equipped with a hydrostatic transmission have the reverse switch mounted on the transmission, next to the selector plate. See Figure 7.18. The Seat Safety Switch is a double pole single throw (DPST) switch. Both poles are normally closed and it is located inside the seat. See Figure 7.20. Selector Figure 7.18 This switch has a yellow wire with black trace connected to it.
CRAFTSMAN Starter solenoid Lighting circuit The starter solenoid is mounted inside the seat box section of the frame. See Figure 7.21. The lighting circuit is hot whenever the engine is running. It receives it's power from the A1 terminal of the key switch. See Figure 7.23. Figure 7.21 Figure 7.23 The starter solenoid can be accessed by removing the battery box and reaching through the opening. See Figure 7.22. Figure 7.
ELECTRICAL Fuse ELECTRICAL The 20A fuse is located inside the seat box section of the frame, on the left side near the deck lift shaft. See Figure 7.24. SYSTEM DIAGNOSIS NOTE: Electrical diagnostic procedures and tools are the same for all Cub Cadet and MTD tractors. This section is written in a way to provide basic trouble shooting skills that can be used on any tractor.
CRAFTSMAN Electronics The outdoor power equipment has historically had relatively simple electro-mechanical controls. Customer expectations and regulatory demands continue to drive change in the industry, while electronic controls have become relatively inexpensive. In many cases, electronic controls can simplify a system that would otherwise be very complex.
ELECTRICAL Electrical environment: AC Vs. DC Most modern outdoor power equipment that has an electrical system complex enough to require diagnosis will be equipped with an alternator that produces alternating current (AC). In most systems, this current is immediately rectified to direct current (DC), and regulated to a nominal 12 Volts. The presence of AC is very limited.
CRAFTSMAN . Kirchhoff's current law: . Kirchhoff's current law deals with nodes. Nodes are the junction of two or more wires or the junction of a wire to a component. Kirchhoff's current law states that what ever current goes into a node must come out. As an example: Three wires are connected with a wire nut. One wire has 5 amps going into the connection. The sum of the currents coming out of the other two wires must equal 5 amps.
ELECTRICAL SYSTEM 7. How the system is wired together The Rules: All circuits have some basic rules that must be followed: 7a. 7b. All circuits must have at least one voltage source. It could be a battery, an altenator or both. All circuits must have a load. A circuit without a load is the same as shorting out the power source.
CRAFTSMAN Series/parallel • Series/parallel Increased resistance circuits have some sections wired in series and some in parallel. See Figure 7.30. Increased resistance is, as the name implies, an increase in resistance. Causes: This can be caused by loose or corroded connections, or connections that are insulated by grease, paint, or coatings. Fasteners finished in oil/phosphate or black oxide are bad conductors. Use bright fasteners (zinc coated).
ELECTRICAL SYSTEM DigitalMulti-meter A DMM is the most useful tool to trouble-shoot any electrical system. There is an amazing variety of DMMs on the market. Some are very basic, others are tailored to specific industries, and some high-end graphing meters function like oscilloscopes. Even the most basic ones are quite versatile. See Figure 7.31. Amperage: Most DMMs have a very limited capacity to test amperage (2-3 Amperes).
CRAFTSMAN Wiringdiagramor schematic A wiring or a schematic diagram, and the ability to read it are very important in troubleshooting a circuit. The diagram shows how the circuit was designed and what paths the electricity is suppose to flow. Fused jumper wires Fused jumper wires are handy to help find bad grounds or to jump across switches for testing purposes. CAUTION: Only use fused jumper wires. If there is a short in the circuit, using an unfused jump could damage components in the circuit.
ELECTRICAL SYSTEM There are two primary reasons to measure amperage: , , To check the out-put of a charging system or battery. To check the performance of a component that draws a substantial flow of power, typically a motor or clutch. Kohler makes a proprietary Rectifier/Regulator tester (Kohler Part Number 25 761 20 and the up-dated version: 25 761 20-S). This tester works on Kohler regulator / rectifiers and the company claims it works on similar systems from other companies. See Figure 7.35.
CRAFTSMAN Testingthe chargingsystem 2b. Quick and dirty test: check voltage across the battery posts using a DMM set to read D.C. voltage with the engine turned-off. It will read battery voltage, typically around 12 V. Start the engine and repeat the voltage measurement. The system voltage should rise, reflecting the out-put of the charging system, typically in the range of 13.0 - 14.5 V.
ELECTRICAL SYSTEM 2e. Interpretation: If the ohm meter indicates no continuity between the two stator leads, there is a fault in the stator windings. If the ohm meter indicates continuity between either stator lead and ground, the stator windings are shorted to ground. Batteries 1. Precautions: See Figure 7.39.
CRAFTSMAN Some charging systems do not work if the system voltage falls below 6V. It takes a certain amount of voltage to excite the fields in the alternator. Solid-state components will not work if the system voltage falls below a given threshold. Some solid-state components can be damaged by the jump-starting that accompanies operation with a dead battery. , • Visual inspection • Electrolyte test • Operational test Visual inspection Inspect the battery and battery connections for corrosion.
ELECTRICAL SYSTEM lb. Give the battery at least ten minutes for the electrolyte to stabilize after charging the battery or adding water to the cells. 10. Measure the temperature of the electrolyte in the middle cells of the battery. ld. Squeeze the bulb on the hydrometer, then insert the hose into the cell. le. Release the bulb, drawing electrolyte into the hydrometer to the fill line.
CRAFTSMAN 2. NOTE:CCA stands for cold cranking amps. The rating should be on the battery for aftermarket batteries. For OEM batteries, contact the manufacturer for the CCA rating. Most riding mower batteries are 200-275 CCA. See Figure 7.41. Fixed load testing Fixed load testers (sometimes called toasters) are inexpensive load testers found at any auto parts store. See Figure 7.42. Figure lf. Record the voltage while the load was applied.
ELECTRICAL SYSTEM 3. Capacitance testing There are several brands of capacitance battery testers presently on the market. Capacitance battery testers use the battery being tested as their power source. These testers send a small AC signal through the battery to measure the capacity of the plate to hold a charge. Capacitance testers are very easy to use and are far less damaging to the battery being tested. For these reasons, capacitance battery testing is the preferred method of battery testing.
CRAFTSMAN , , 4e. If the battery is being checked independently of the equipment it powers, measure and note the battery voltage while it is disconnected, over a three-day period. 4f. There should be less than a .2 volt drop in the readings. If there is more than a .2 volt drop, the battery is bad. Always store a battery with a full charge (unless the battery is a dry battery and the electrolyte has not been added yet). This may require periodic re-charging. 5b.
ELECTRICAL SYSTEM 7a. Starting with a fully charged battery and battery cable connections that are clean and tight, measure the battery voltage. See Figure 7.46. Voltage Drop Test To review: Ohm's law states that it takes voltage to push current through a resistance. Kirchhoff's voltage law states that the sum of all the voltage drops equals the source voltage. Combining those two laws, we see that any restriction in a circuit (e.g.
CRAFTSMAN , , The voltage that shows-up on the meter is the voltage that is being used to pass current through a resistance in the circuit. Voltage drop on a good circuit should be less than 0.1 volts. A voltage drop reading on the meter of greater than 0.2 volts indicates a fairly substantial problem that demands attention. As an example, if the starter solenoid does not engage properly, check for voltage drop between the ground point for the starter solenoid and the negative post on the battery.
ELECTRICAL SYSTEM 16. Voltage drop on a good circuit should be less than 0.1 volts. A voltage drop reading on the meter of greater than 0.2 volts indicates a fairly substantial problem that demands attention. Testing switches • Refer to the "Components" section of this chapter that describes the function of the individual switches to be tested. As an example, if the tractor had a slow-turning starter, the ground-side voltage drop measured below 0.
CRAFTSMAN The male spade terminals that are associated with each-other face each-other broad-surface to broad surface. See Figure 7.52. Relay Most of the relays used by MTD or Cub Cadet have five pins. See Figure 7.53. Normally Closed switch element: Spades marked: "NC" qormally Open switch element: Figure 7.52 Figure 7.53 Windings: Terminals 1 & 2 are the outer-most of the row of three small spade terminals. When one has power and the other is connected to ground, the relay is energized.
ELECTRICAL SYSTEM To test a relay: , , Test for continuity between the common and the NC terminals using a DMM. Test for continuity between the common and the NO terminals using a DMM. Diodes What is a diode? A diode acts like a one way valve, allowing current to flow in only one direction. See Figure 7.54. NOTE: There should be continuity with the NC terminal and no continuity for the NO terminal. If the results vary from this the relay is bad. , , Silver band Apply 12 volts to terminals 1 and 2.
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 , 7. Switch the leads. The meter should indicate no continuity. See Figure 7.57. No continuity Silver band Figure 7.57 , 38 If the results do not match the above, replace the diode.
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