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  • ELECTRICAL

    25 & 30 TON ARTICULATED DUMP TRUCKS 1

    CASE 325 & 330 ARTICULATED DUMP TRUCKS

    Electrical

  • ELECTRICAL

    25 & 30 TON ARTICULATED DUMP TRUCKS 2

    CNH America LLC © 2004 700 STATE STREET RACINE, WI 53404 U.S.A. Printed in U.S.A.

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    25 & 30 TON ARTICULATED DUMP TRUCKS 3

    Table of Contents Test Equipment ...................................................................................................5 Test Procedures ..................................................................................................8 Legends and Symbols ......................................................................................14 Relay and Fuse Identification and Location ...................................................17 Electrical Legend ..............................................................................................23 Power control and Distribution, Batteries, Alternator, Key Switch ..............26 Headlights, High Beam, Low Beam, Clearance, & Fog Light Circuits ..........30 Hazard and Directional Lights Circuits ...........................................................34 Indicator Lamps, Dash Panel ...........................................................................35 Mirror-Hood-AC, Mirror Alignment Motors & Heating, AC Circuit ................40 TV Monitor and Gauges....................................................................................42 Working Lights and Windshield Wipers..........................................................44 Differential Lock Switch Circuit .......................................................................44 Body Unloading Hoist and Transmission Kick Down Circuits......................46 Parking Brake Circuit........................................................................................46 Ejector Circuit (Optional)..................................................................................46

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    25 & 30 TON ARTICULATED DUMP TRUCKS 4

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    25 & 30 TON ARTICULATED DUMP TRUCKS 5

    Electrical Test Equipment

    Electrical Testing The most important aspect of troubleshooting today’s sophisticated electrical and/or electronic systems is the test results. A service technician must have confidence in his testing equipment to get accurate readings.

    The days of checking a system with a test light are past. Electronic equipment runs on very low amperage, and a test light can draw enough amperage to burn out a circuit in a control box. Today’s electronics will run on variable voltages. Just because the machine has 24- volt batteries does not mean the system is running on 24 volts. Most machines will have 24, 12, 8 and 5-volt circuits. With different voltages being used, a test light will be useless. The only way to test a circuit is with an electronic voltmeter and an ohmmeter.

    The Electronic Voltmeter should be used to do all electrical testing and trouble shooting. Remember that the circuit must be fully connected and operated to get proper test results. You should be looking for voltage drops to determine where the problem is. You must also be aware of how the system functions. If the system shuts down after automatically detecting a fault, you cannot test the circuit for proper system voltage. An Ohmmeter should be used when a voltmeter cannot be used for some reason. The ohmmeter should only be used when checking components or circuits that have a specified resistance. An example would be a solenoid that may have a specified resistance of 7 to 9 ohms; an ohmmeter is the proper tool to be used.

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    25 & 30 TON ARTICULATED DUMP TRUCKS 6

    Listed below is an abbreviated list of electrical tools that can be purchased locally or through the OTC tool catalog.

    Piercing Clips may be used to test for voltage in the harness with out

    damaging the wires.

    An example would be: Piercing Clips Fluke 1TC26 Alligator Clips Fluke 1TC21

    Leads 1TC08 Digital Volt/Ohm Meter; An example would be a Fluke 23 Replacement Probes

    Fundamentals of Testing an Electrical System Before any testing is done to the electrical system in question, the service technician must fully understand how the entire system (electrical and hydraulic) functions normally. In many instances, the operation of the system may only need to be explained to the operator, or a simple adjustment made to the system for it to function properly. Referencing the appropriate operator’s manual will generally resolve these types of problems. When searching for the cause of an electrical problem, it is desirable to obtain all of the symptoms of the problem from the operator. A few pertinent questions asked of the operator may give you valuable clues as to the cause of the problem. While questioning the operator, a chance remark may well reveal the cause of the problem to an alert service technician. Operate the equipment to see if you can duplicate the problem.

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    25 & 30 TON ARTICULATED DUMP TRUCKS 7

    Utilize the easiest and simplest tests first to try to identify the problem. When it has been determined that a problem does exist with the electrical system, the service technician must understand the fundamentals of electricity. Understanding the properties of voltage, current and resistance is a must. The service technician has to be equipped with the proper testing equipment to resolve the problem. Use of the digital multimeter is strongly recommended. However, just having the equipment is not enough, the service technician must understand and utilize the functions and features of the digital multimeter! Once the problem has been identified, correct repair procedures must be followed to insure that the problem does not reoccur. Use of the Electrical Connector and Terminal Repair Kit, is strongly recommended. The kit is equipped with the necessary tools and connectors for proper repairs as well as information on how to utilize the repair tools in the kit.

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    25 & 30 TON ARTICULATED DUMP TRUCKS 8

    Test Procedures

    Visual Inspection Carefully inspect the complete wiring harness for damage. Check for loose or broken wires. Make sure the connector terminals are fully seated and locked in the connector. Insure that the terminals are clean and not damaged. Use of Lectra Clean, is recommended, and Silicone Compound Dielectric Grease, can be used for lubricant and corrosion protection. Testing For “Open” Circuits An “open” circuit is defined as a place in a circuit that is separated and does not permit a path for electrical current to flow. This could be a disconnected connector or a broken wire. Because the circuit is open, the circuit resistance, when measured with a Digital Multimeter, will indicate infinite resistance (OL or Open Lead). Test for continuity through each wire using a digital multimeter. Use wire colors or connector pin identification numbers to identify the wires at each end of the harness. If the harness is long and both ends cannot be reached, connect two pins together at one connector with a jumper wire. Test for continuity through the wires at the other connector. Repeat this process by moving the jumper wire as needed until all wires are checked. Finding an “Open” Circuit Using a digital multimeter set to the ohms (Ω) scale, connect one probe to each end of the broken wire. Move along the length of the harness, flexing the harness by hand, while watching the Multimeter. Any change on the ohmmeter indicates the damaged area has been located. If the damage cannot be located, find the approximate middle of the harness length. Carefully cut the outer jacket of the harness to reach the wire to be tested. Insert a needle or pin through the wire insulation and connect the meter to the needle or pin. Test for continuity between the middle and the end of the wire. If there is continuity, move to another test point farther down the wire and test again. When no continuity is obtained, the break in the circuit will be between the last points tested which will permit the exact location to be determined. If the cable is strapped down, it will be necessary to add a length of wire to one probe of the ohmmeter to lengthen the meter leads.

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    25 & 30 TON ARTICULATED DUMP TRUCKS 9

    “Opens”

    A ________________ A B ________________ B C ________________ C D ________________ D E _______ ______ E F ________________ F

    G _______ ______ G H ________________ H I _________________ I J ______ ______ J K _________________ K L _________________ L

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    25 & 30 TON ARTICULATED DUMP TRUCKS 10

    Testing For Short Circuits

    A “short” circuit is defined as an unintended, low resistance current path. This means that the current is taking a “shorter” path than was intended in the original circuit. This could be a result of two or more wires rubbing together (copper to copper) or a wire rubbing the system ground (copper to iron). This results in the shorted circuit having resistance much smaller than specifications as show

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