This lesson will instruct the student on how to inspect and test A/C-heater control panel assembly, inspect and test A/C-heater control cables, motors, and linkages, and determine/perform necessary action. Knowledge of these techniques and the skills required to correct problems associated with this task are necessary for a student to acquire if they wish to compete for high paying, high skilled jobs in an Automotive Repair Facility. Entry level technicians need to be able to perform this task to 100% accuracy. Incorrectly performing this task can lead to an automobile accident or create customer satisfaction issues.
Inspect and test A/C-heater control panel assembly, Inspect and test A/C-heater control cables, motors, and linkages; determine/perform necessary action.
Given the proper tools and instruction, the student will be able to inspect and test A/C-heater control panel assembly, inspect and test A/C-heater control cables, motors, and linkages, determine/perform necessary action, and pass a written test covering the task with 100% accuracy.
Instruct students that the control panel is found in the instrument panel at a convenient location for both driver and front-seat passenger access. Explain that three types of control panels may be found: manual, push-button, or touch pad. Let them know that all serve the same purpose. They provide operator input control for the air-conditioning and heating system. Tell students that some control panels have features that other panels do not have such as provisions to display in-car and outside air temperature in degrees
Inform students that at times the control panel is the root of problems. Tell them to inspect the connectors to the control unit, and look for damage and corrosion. With on ohmmeter, instruct students to check the continuity through the blower motor switch in all of its positions. Tell them to compare their results with the wiring diagram for the switch. Also, tell them to check the resistance across the temperature control switch.
Instruct students that if the mode selector switch is electrical, they should check for continuity across the terminals as they move the switch through the various mode selections. If the mode selector switch is a vacuum switch, tell them to apply a vacuum to the inlet of the switch and feel for a vacuum at the various tube connectors on the switch while they move the selector through its various positions. Tell them to compare their results to the information in the service manual.
Explain that the ATC control panels are not repaired; rather, they are replaced as a unit. Let students know that care needs to be taken when replacing these units. Like the other electronic circuits on a vehicle, the control panel may be part of the BCM circuit. Tell them to follow all precautions to eliminate static and voltage spikes at the BCM.
Have them look for disconnected or broken hoses, broken connectors, misrouted vacuum lines, and loose or disconnected electrical connectors at vacuum switches and controls. Tell them identify the vacuum source for the various doors and switches of the duct system and make sure vacuum is available when the engine is running. Inform them to disconnect that vacuum source, connect a vacuum gauge to the inlet for the defroster door motor(s) and record the vacuum available there when the master control switch is in the following positions: max, norm, bi-level, vent, heat, blend, defrost, and off. If they do not move with the engine’s vacuum, tell students to use a hand-operated vacuum pump to check the component’s activity and its ability to hold a vacuum. Also let them know to use the vacuum pump to check all one-way check valves.
Instruct students to check all mechanical or cable linkages and controls. Tell them to make sure the cables are properly attached to the levers of the control switch. If the cable(s) is equipped with an automatic adjuster, remind students to make sure the adjusting mechanism operates freely and is not damaged.
Inform students that if they are dealing with blend and mode door servomotors, they should not move blend or mode doors manually, as this may cause damage. Tell them that blend and mode doors can be repositioned through an onboard diagnostic program with a scan tool on some systems. On other systems, let them know that sensors may need to be disconnected or harness terminals jumpered to move the blend doors. Tell them to refer to the appropriate Service Manual for moving the blend and mode doors to check alignment in all positions.
Tell students that an electronically controlled, high-torque servomotor normally produces a low, humming sound as the blend door moves. Explain that if the servomotor does not move, they should check for proper voltage to the servomotor and for proper grounding. If voltage is available, but the servomotor does not rotate, tell students to check for obstructions at the blend or mode door or binding in the linkage before condemning the motor.
Evaluation and feedback Prior to Testing or Lab Work
Objective 1. / Formative assessment / Instructor will observe students as they practice the procedure to assure correct procedure and safety practices are being followed. A checklist will be utilized to chart student progress on the task. Questioning techniques will be utilized as necessary to demonstrate student comprehension / Adaptations and/or accommodations for special needs students will be added if required.
STUDENT ASSESSMENT: (Assess student progress with performance criteria.)
Objective 1 / Summative assessment / written test questions on stated objective / adaptation and / or accommodations for special needs students will be added if required
IMPACT--Reflection/Analysis of Teaching and Learning: (How did students’ progress in relation to the state objectives? Was the instruction successful? Analyze samples of student work particularly that which is unsatisfactory, for the purpose of planning further instruction.)
REFINEMENT--Lesson Extension and Follow-up: (To be filled in as the lesson is modified during initial planning and/or during the teaching learning process.)