HDD 207 - Heavy Duty Diesel Heating, Ventilation, & Air ConditiioningCredits: 4
Instructional Contact Hours: 6
Introduces and practices the service of heavy duty diesel vehicle heating, ventilation, and air conditioning (HVAC) systems. Practices NATEF tasks related to HVAC systems of heavy duty diesel vehicle.
Prerequisite(s): HDD 202 and HDD 206 both with a minumum grade of "C" (2.0)
Corequisite(s): HDD 203W , HDD 209W , and HDD 210
Lecture Hours: 60 Lab Hours: 30
Meets MTA Requirement: None
Pass/NoCredit: Yes
Outcomes and Objectives 1: Complete general HVAC system diagnosis and related NATEF tasks as listed below.
A. Verify the need for service or repair of HVAC systems based on unusual operating noises; determine needed action.
B. Verify the need for service or repair of HVAC systems based on unusual visual, smell, and touch conditions; determine needed action.
C. Identify system type and components (cycling clutch orifice tube – CCOT, expansion valve) and conduct performance test(s) on HVAC
systems; determine needed action.
D. Retrieve diagnostic codes; determine needed action.
2. Complete NATEF tasks related to A/C System and Components as listed below.
A. A/C System - General
1. Identify causes of temperature control problems in the A/C system; determine needed action.
2. Identify refrigerant and lubricant types; check for contamination; determine needed action.
3. Identify A/C system problems indicated by pressure gauge and temperature readings; determine needed action.
4. Identify A/C system problems indicated by visual, audible, smell, and touch procedures; determine needed action.
5. Perform A/C system leak test; determine needed action.
6. Recover, evacuate, and recharge A/C system using appropriate equipment.
7. Identify contamination in the A/C system components; determine needed action.
8. Interface with vehicle's on-board computer; perform diagnostic procedures using recommended electronic service tool(s) (including PC
based software and/or data scan tools); determine needed action.
B. Compressor and Clutch
1. Identify A/C system problems that cause protection devices (pressure, thermal, and electronic) to interrupt operation; determine
needed action.
2. Inspect, test, and replace A/C system pressure, thermal, and electronic protection devices.
3. Inspect and replace A/C compressor drive belts, pulleys, and tensioners; adjust belt tension and check alignment.
4. Inspect, test, adjust, service, or replace A/C compressor clutch components or assembly.
5. Inspect and correct A/C compressor lubricant level (if applicable).
6. Inspect, test, or replace A/C compressor.
7. Inspect, repair, or replace A/C compressor mountings and hardware.
C. Evaporator, Condenser, and Related Components
1. Correct system lubricant level when replacing the evaporator, condenser, receiver/drier or accumulator/drier, and hoses.
2. Inspect A/C system hoses, lines, filters, fittings, and seals; determine needed action.
3. Inspect and test A/C system condenser. Check for proper airflow and mountings; determine needed action.
4. Inspect and replace receiver/drier or accumulator/drier.
5. Inspect and test cab/sleeper refrigerant solenoid, expansion valve(s); check placement of thermal bulb (capillary tube); determine
needed action.
6. Remove and replace orifice tube.
7. Inspect and test cab/sleeper evaporator core; determine needed action.
8. Inspect, clean, or repair evaporator housing and water drain; inspect and service/replace evaporator air filter.
9. Identify and inspect A/C system service ports (gauge connections); determine needed action.
10. Identify the cause of system failures resulting in refrigerant loss from the A/C system high pressure relief device; determine needed
action.
3. Complete NATEF tasks related to Heating and Engine Cooling Systems as listed below.
A. Identify causes of outlet air temperature control problems in the HVAC system; determine needed action.
B. Identify window fogging problems; determine needed action.
C. Perform engine cooling system tests for leaks, protection level, contamination, coolant level, coolant type, temperature, and conditioner
concentration; determine needed action.
D. Inspect engine cooling and heating system hoses, lines, and clamps; determine needed
E. Inspect and test radiator, pressure cap, and coolant recovery system (surge tank); determine needed action.
F. Inspect water pump; determine needed action.
G. Inspect and test thermostats, by-passes, housings, and seals; determine needed repairs.
H. Recover, flush, and refill with recommended coolant/additive package; bleed cooling system.
I. Inspect thermostatic cooling fan system (hydraulic, pneumatic, and electronic) and fan shroud; replace as needed.
J. Inspect and test heating system coolant control valve(s) and manual shut- off valves; determine needed action.
K. Inspect and flush heater core; determine needed action.
4. Complete NATEF tasks related to Operating Systems and Related Controls as listed below.
A. Electrical
1. Identify causes of HVAC electrical control system problems; determine needed action.
2. Inspect and test HVAC blower motors, resistors, switches, relays, modules, wiring, and protection devices; determine needed action.
3. Inspect and test A/C compressor clutch relays, modules, wiring, sensors, switches, diodes, and protection devices; determine needed
action.
4. Inspect and test A/C related electronic engine control systems; determine needed action.
5. Inspect and test engine cooling/condenser fan motors, relays, modules, switches, sensors, wiring, and protection devices; determine
needed action.
6. Inspect and test electric actuator motors, relays/modules, switches, sensors, wiring, and protection devices; determine needed action.
7. Inspect and test HVAC system electrical/electronic control panel assemblies; determine needed action.
8. Interface with vehicle’s on-board computer; perform diagnostic procedures using recommended electronic service tool(s) (including PC
based software and/or data scan tools); determine needed action.
B. Air/Mechanical
1. Identify causes of HVAC air and mechanical control problems; determine needed action.
2. Inspect and test HVAC system air and mechanical control panel assemblies; determine needed action.
3. Inspect, test, and adjust HVAC system air and mechanical control cables and linkages; determine needed action.
4. Inspect and test HVAC system actuators and hoses; determine needed action.
5. Inspect, test, and adjust HVAC system ducts, doors, and outlets; determine needed action.
5. Complete NATEF tasks related to Refrigerante Recovery, Recycling, and
A. Maintain and verify correct operation of certified equipment.
B. Identify and recover A/C system refrigerant.
C. Recycle or properly dispose of refrigerant.
D. Handle, label, and store refrigerant.
E. Test recycled refrigerant for non-condensable gases.
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