HEMT

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Occupational Title: Heavy Equipment Maintenance Technician
Key Purpose: Diagnose, service and repair heavy equipment

Critical Work Function
5 Diagnose, service, and repair vehicle air brake
systems

Occupational Skills, Knowledge and Conditions

Key Activities

Performance Criteria

Occupational Skills and Knowledge

Conditions

Those duties or task clusters that are necessary to perform each critical work function.

Specific demonstrable performance and standards that indicate when the key activity has been performed successfully.

Those skills and knowledge that are specific to the occupation, such as technical processes or procedures common across the occupation that are critical to the related key activity.

Tools, resources and equipment necessary to carry out key activities and their related performance criteria.

KA
5.1

Inspect, diagnose, service, repair, and adjust brake systems.

Number	Criteria
5.1.1	Inspect brake system operation for adjustment, wear, and general condition.
5.1.2	Diagnose poor stopping, brake noise, pulling, grabbing, or dragging complaints.
5.1.3	Diagnose, service, repair, and adjust air components.
5.1.4	Diagnose, service, repair, and adjust hydraulic brake components.
5.1.5	Post-service vehicle performance indicates system components performing at or above OEM specifications.

Knowledge of brake system
components and parts and explain their function (slack adjusters, brake spider, brake drum, and brake rotor)

Knowledge and understanding of braking theory and operation

Knowledge of wedge brake system components (housing, plungers, assembly, spider, and adjusting plungers)

Understanding of air-disc brake assemblies and multiple disc-brake assemblies

Knowledge of brake-system component inspection and testing (pedal push rod, master cylinder, valves, light switches, brake caliper, booster, and controls)

Understanding of brake system bleed/flush processes

Knowledge and usage of shop manuals and other appropriate documentation

Using the following tools, resources, and equipment:

Appropriate service tools and testing equipment

Common mechanic's hand tools

Appropriate shop service manuals and other documentation

KA 5.2

Diagnose, service, repair, and adjust parking brakes.

Number	Criteria
5.2.1	Diagnose, service, repair, and adjust drum/disc-application brake systems.
5.2.2	Diagnose, service repair, and adjust spring-brake systems.
5.2.3	Post-service vehicle performance indicates system components performing at or above OEM specifications.

Knowledge of parking-brake system components and parts and explain their function

Knowledge and understanding of parking-brake theory and operation

Knowledge of drum/disc parking-brake system components (drums, rotors, adjustors, and mounting hardware)

Knowledge of spring-brake parking-brake system components (chamber diaphragms, manual release, release valves, and check valves)

Knowledge and ability to read schematics of parking-brake system (electronics, hydraulic)

Knowledge and usage of shop manuals and other appropriate documentation

Using the following tools, resources, and equipment:

Common mechanic's hand tools

Appropriate service tools and testing equipment

Appropriate shop service manuals and other documentation

KA
5.3

Diagnose, service, and repair ABS (anti-locking braking) systems.

Number	Criteria
5.3.1	Diagnose, adjust, service, and replace wheel speed sensors, wires, and connectors.
5.3.2.	Diagnose, service, and replace ABS controllers, wires, cables, and connectors.
5.3.3	Diagnose, service, and replace ABS valve assembly.
5.3.4	Diagnose, service, and replace Automatic Traction Control.
5.3.5	Post-service vehicle performance indicates system components performing at or above OEM specifications.

Knowledge and understanding of ABS system components and parts

Knowledge of PC usage and ABS diagnostic software

Knowledge of and ability to read ABS schematics

Knowledge and usage of shop manuals and other appropriate documentation

Using the following tools, resources, and equipment:

Personal/laptop computer

ABS diagnostic software

Common mechanic's hand tools

Appropriate service tools and testing equipment

Appropriate shop service manuals and other documentation

KA
5.4

Inspect and test air system components.

Number	Criteria
5.4.1	Perform vehicle air system inspection in accordance with state and federal regulations.
5.4.2	Perform pressure tests and leak to determine needed repairs.
5.4.3	Perform governor cut-in/cut-out tests to determine needed repairs.
5.4.4	Perform safety and check-valve tests to determine needed repairs.
5.4.5	Perform air system operational tests to determine needed repairs.
5.4.6	Check for oil, water, and contaminants in reservoirs to determine needed repairs.
5.4.7	Conduct air-starting system performance tests and determine needed repairs.
5.4.8	Diagnose, remove, repair, and install/replace air starter.
5.4.9	Diagnose, remove, repair, and install/replace air-starter valves and controls.
5.4.10	Perform cold weather air system maintenance.
5.4.11	Inspect, align, adjust, or replace compressor drive belts and pulleys
5.4.12	Inspect, time, or replace compressor drive gear and coupling.
5.4.13	Diagnose, service, repair, or replace air compressor, air cleaner, and connecting lines and fittings.
5.4.14	Post-service performance indicates system components performing at or above OEM specifications.

Knowledge of air system components and parts and their function

Understand and interpret air system schematics

Knowledge of air-system device controls and their function

Knowledge of air-system components and parts and their function

Knowledge and application of appropriate testing gauges

Knowledge and usage of shop manuals and other appropriate documentation

Using the following tools, resources, and equipment:

Common mechanic's hand tools

Appropriate service tools and testing equipment

Air pressure test gauge and fittings

Belt tension gauge

120 PSI air source

Air pressure test gage (O-ISO PSI) and fittings

Appropriate shop service manuals and other documentation