• MEM18030B - Diagnose and rectify low voltage electrical systems

MEM18030B
Diagnose and rectify low voltage electrical systems

This unit covers using test instruments, testing the battery, and assessing and rectify wiring faults.

Application

This unit applies to testing and rectification activities associated with 12, 24 and 36 volt wiring systems on vehicles, plant and stationary equipment. The system extends to wiring, switching mechanisms and circuit protection devices.

This unit should not be selected with any of the following Units: Unit MEM18045B (Fault find/repair electrical equipment/components up to 250 volts single phase supply), or Unit MEM18046B (Fault find/repair electrical equipment/components up to 1000 volts a.c./1500 volts d.c.

Except in exceptional circumstances this unit should not be selected with Unit MEM18056B (Diagnose and repair analog equipment and components) or Unit MEM18066B (Diagnose and repair microprocessor based equipment).

If soldering of wires/connections is required, see Unit MEM05001B (Perform manual soldering/desoldering - electrical/electronic components).

Band: A

Unit Weight: 8


Prerequisites

Path 1

MEM09002B

Interpret technical drawing

MEM12023A

Perform engineering measurements

MEM18001C

Use hand tools

MEM18002B

Use power tools/hand held operations

MEM18055B

Dismantle, replace and assemble engineering components


Elements and Performance Criteria

ELEMENT

PERFORMANCE CRITERIA

1. Use test instruments

1.1. Electron theory, current, voltage and resistance principles are understood.

1.2. Appropriate test instruments are selected, used and maintained to determine current, voltage and resistance.

1.3. Electrical drawings and manufacturers' diagrams are correctly interpreted.

1.4. Series, parallel and series parallel circuits are correctly determined.

1.5. Basic electrical laws are understood and correctly applied.

1.6. AVR test instruments are correctly connected into circuits.

1.7. Meters are read to standard accuracy; and wave form and quantities are determined using general purpose oscilloscope.

1.8. Multipliers and shunts are correctly used and applied.

2. Test battery

2.1. Chemical battery operating principles are understood.

2.2. Electrolyte level is correctly determined and specific gravity readings temperature is corrected.

2.3. Dry charge preparation and recharging of batteries is carried out correctly.

2.4. Discharge testing is performed according to prescribed procedures.

2.5. Replacement batteries are correctly selected for application.

3. Assess and rectify wiring faults

3.1. Wiring faults are correctly isolated.

3.2. Replacement cables/wires are correctly sized.

3.3. Insulation quality is correctly determined.

3.4. Wiring looms are correctly made up for application and securely fixed.

3.5. Wiring terminations are stripped, fitted, prepared and made correctly.

3.6. Corrosion is removed, neutralised and appropriate protective coating is applied.

3.7. Relays, solenoids, contacts and circuits are correctly tested and repaired/replaced.

Required Skills

Required skills

Look for evidence that confirms skills in:

reading, interpreting and following information on written job instructions, specifications, standard operating procedures, charts, lists, drawings and other applicable reference documents

planning and sequencing operations

checking task-related information

checking for conformance to specification

selecting and using the correct test instrument for a variety of electrical circuits, to measure the current, voltage and resistance of specified circuit components or sections of circuitry

applying Ohm's law to determine the required values of voltage, current and resistance for a range of electrical circuits

determining the resistance of series and parallel circuits

connecting electrical test instruments into given circuits to determine the required values of current, voltage and resistance

connecting and adjusting a general purpose oscilloscope to a given electrical circuit to measure wave forms at nominated points in the circuit

determining the specific gravity of the electrolyte for temperature variations

preparing dry batteries for charging and recharging

performing discharge testing of batteries

testing given electrical circuits and, where appropriate, identifying wiring faults

using supplier catalogues

making up wiring looms

terminating wiring

removing and/or neutralising corrosion from terminals and connections, and applying appropriate protective coatings

testing a range of circuit components for correct operation and identifying and repairing faulty circuit components

Required knowledge

Look for evidence that confirms knowledge of:

the principles of electron theory

definitions of current, voltage and resistance in terms of electrical circuits

the relationships between current, voltage and resistance for a variety of given electrical circuits

the instruments and procedures to be used to measure current, voltage and resistance

the procedures for maintaining electrical test equipment

the function of a variety of electrical circuits identified from given electrical drawings/diagrams

the symbols used in electrical drawings/diagrams

the components of a variety of electrical circuits identified by given electrical drawings/diagrams

the differences between series and parallel electrical circuits

the function of a general purpose oscilloscope and procedures for connecting a general purpose oscilloscope into given electrical circuits

the use of wave forms in the testing of electrical circuits

the accuracy to which a range of electrical test equipment can be read

the procedures for using multipliers and shunts in the measurement of electrical circuits

the operation of a chemical battery

the function of the electrolyte in batteries

the procedures for measuring the specific gravity of the electrolyte

the effect of temperature on the specific gravity of the electrolyte

the procedures for preparing dry batteries for charging

the procedures for recharging batteries

hazards and control measures associated with charging/recharging of batteries and discharge testing, including housekeeping

the purpose and procedures for discharge testing of batteries

the specifications applied to batteries

examples and causes of common faults in electrical wiring

the test procedures for isolating wiring faults

the specifications of cables and wires used in given electrical circuits

the specification of the insulation materials

the procedures for making up and fixing wiring looms can be given.

the procedures for stripping, fitting and preparing wiring terminations

the procedures for soft and hard soldering/crimping of wiring terminations

the effect of corrosion on the performance of electrical circuits and connections

the procedures for corrosion removal and/or neutralisation

coatings available to stop/inhibit corrosion

the correct operational relays, solenoids and contacts

common faults and causes in relays, solenoids, contacts and circuits

the procedures for testing circuit components

safe work practices and procedures

Evidence Required

The evidence guide provides advice on assessment and must be read in conjunction with the performance criteria, required skills and knowledge, range statement and the Assessment Guidelines for the Training Package.

Overview of assessment

A person who demonstrates competency in this unit must be able to test and rectify low voltage electrical systems. Competency in this unit cannot be claimed until all prerequisites have been satisfied.

Critical aspects for assessment and evidence required to demonstrate competency in this unit

Assessors must be satisfied that the candidate can competently and consistently perform all elements of the unit as specified by the criteria, including required knowledge, and be capable of applying the competency in new and different situations and contexts.

Context of and specific resources for assessment

This unit may be assessed on the job, off the job or a combination of both on and off the job. Where assessment occurs off the job, that is the candidate is not in productive work, then an appropriate simulation must be used where the range of conditions reflects realistic workplace situations. The competencies covered by this unit would be demonstrated by an individual working alone or as part of a team. The assessment environment should not disadvantage the candidate.

This unit could be assessed in conjunction with any other units addressing the safety, quality, communication, materials handling, recording and reporting associated with testing and rectifying low voltage electrical systems or other units requiring the exercise of the skills and knowledge covered by this unit.

Method of assessment

Assessors should gather a range of evidence that is valid, sufficient, current and authentic. Evidence can be gathered through a variety of ways including direct observation, supervisor's reports, project work, samples and questioning. Questioning techniques should not require language, literacy and numeracy skills beyond those required in this unit of competency. The candidate must have access to all tools, equipment, materials and documentation required. The candidate must be permitted to refer to any relevant workplace procedures, product and manufacturing specifications, codes, standards, manuals and reference materials.

Guidance information for assessment


Range Statement

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation, needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Test instruments

Multimeters, amp meters, circuit testers


Sectors

Unit sector


Competency Field

Maintenance and diagnostics


Employability Skills

This unit contains employability skills.


Licensing Information

Not Applicable