project 2: job 6—diagnose an air conditioning system · pdf file... job 6—diagnose...

Name ________________________________________________________ Date _________________

Instructor _____________________________________________________ Period ________________

49Copyright by Goodheart-Willcox Co., Inc.

After completing this job, you will be able to inspect a vehicle refrigeration system and test the system for leaks.

Instructions

As you read the job instructions, answer the questions and perform the tasks. Print your answers neatly and use complete sentences. Consult the proper service literature and ask your instructor for help as needed.

WarningBefore performing this job, review all pertinent safety information in the text and discuss safety procedures with your instructor.

Procedures

1. Obtain a vehicle to be used in this job. Your instructor may direct you to perform this job on a shop vehicle.

2. Gather the tools needed to perform the following job. Refer to the project’s tools and materials list.

3. Obtain the proper service information and determine the type of refrigeration system used:

• Cycling clutch and orifice tube. ___

• Capacity control compressor and orifice tube. ___

• Expansion valve system. ___

• Expansion valve system with evaporator pressure control. ___

4. Determine the system pressure specifications in the service manual. Write the pressures in the spaces provided.

Low side: _______________

High side: _______________

Visually Inspect the Air Conditioning System 1. Open the vehicle hood.

2. Visually check the refrigeration system for obvious refrigerant leaks. Leaks are indicated by oil on refrigeration system parts.

Did you find any leaks? Yes ___ No ___

If Yes, describe the leak locations: __________________________________________________

WarningIf you are working on a hybrid vehicle, prevent potentially fatal shocks by performing step 3 before beginning any service operations. Check the vehicle service information for exact procedures. Skip step 3 if the vehicle is not a hybrid type.

Project 2: Job 6—Diagnose an Air Conditioning System

VII.A.2

VII.B.1

VII.B.5

50 Copyright by Goodheart-Willcox Co., Inc.

3. Disable hybrid vehicle high-voltage system, if applicable.

a. Identify the vehicle’s low- and high-voltage circuits. Consult the manufacturer’s service infor-mation as necessary.

NoteThe high-voltage cables on many hybrid vehicles are covered with orange insulation for easy identification.

b. Disable the high-voltage circuit by one of the following methods:

• Check the vehicle service information for exact location of the auxiliary battery negative terminal and disconnect the clamp.

• Check the vehicle service information for exact location of the service disconnect plug and remove it.

• Remove the specific high-voltage circuit control fuse or control relay.

CautionWear insulated rubber gloves when removing any of the above electrical components.

c. Wait at least 5 minutes to allow the full discharge of the high-voltage condensers.

d. Using a voltmeter or multimeter, test the high-voltage cables for low or zero voltage. Less than 12 volts is considered safe.

4. Examine the air conditioner compressor drive belt, tensioning devices, and pulleys.

NoteSkip this step if the compressor is driven by an electric motor.

Is the compressor drive belt condition acceptable? Yes ___ No ___

If No, describe the damage: _______________________________________________________

Is the compressor drive belt tension acceptable? Yes ___ No ___

If No, and the belt is a V-belt, tighten the belt. Refer to Job 23 for information on setting belt tension. If the belt is a serpentine belt, inspect the belt tensioner for the following defects:

• Weak tensioner spring resistance.

• Worn pulley grooves.

• Worn bearings (roughness when turning the tensioner).

Can the tensioner be reused? Yes ___ No ___

If No, explain why not: __________________________________________________________

Are the belt pulleys bent, or otherwise damaged? Yes ___ No ___

If No, describe the pulley defect: ___________________________________________________

Are the belt pulleys properly aligned? Yes ___ No ___

Are the pulleys and belts aligned? Yes ___ No ___

If No, describe the relative positions of the pulleys: ____________________________________

Project 2: Job 6—Diagnose an Air Conditioning System (continued)

VII.B.2

Name ________________________________________________________


5. Examine the refrigeration hoses and fittings.

Is frayed rubber evident on any hoses? Yes ___ No ___

Are cuts evident on any hoses? Yes ___ No ___

Did you find evidence of leaks on any of the hoses or at any fittings? Yes ___ No ___

Are any of the refrigerator hose fittings damaged? Yes ___ No ___

If you answered Yes to any of these questions, describe the defects: ________________________

6. Check the other accessible air conditioning system components for defects.

Does the compressor clutch appear to be in good condition? Yes ___ No ___

If No, describe the defects: ________________________________________________________

Does the compressor clutch have excessive clearance? Yes ___ No ___

If Yes, consult your instructor.

Do you see any dirt or other debris on the condenser? Yes ___ No ___

If Yes, carefully clean the condenser.

Do you see any visible damage to condenser or accumulator/receiver-drier? Yes ___ No ___

If Yes, describe the damage: _______________________________________________________

Is the evaporator drain obstructed? Yes ___ No ___

NoteIf condensation is dripping from under the vehicle, it can be assumed that the drain is open. However, if sloshing noises are heard or the front carpet of the vehicle is wet, make a visual check of the drain hose.


Is refrigerant oil visible? Yes ___ No ___


Determine the Type of Refrigerant Used 1. Consult the appropriate service literature and check the vehicle’s refrigerant identification sticker

to answer the following questions.

Identify the original refrigerant used in the vehicle: ____________________________________

Does the vehicle have a retrofit label? Yes ___ No ___

If Yes, what refrigerant was used to replace the original refrigerant? _______________________

2. Obtain a refrigerant identifier and calibrate it according to manufacturer’s instructions. See Figure 6-1.

Type of refrigerant identifier used: __________________________________________________

3. Remove the service valve caps and install a refrigerant identifier on one service port.

Project 2: Job 6 (continued)

VII.B.7

VII.B.3

VII.B.8

VII.B.11

VII.A.7

VII.E.2


4. Turn on the refrigerant identifier and record the type(s) of refrigerant in the system. If there are multiple types of refrigerant present, record the percentage of each:

Refrigerent Type Percentage____________________ ____________________

____________________ ____________________

____________________ ____________________

____________________ ____________________

____________________ ____________________

Are any unknown refrigerants or contaminants present? Yes ___ No ___

If Yes, record the amount (percentage) of unknown refrigerants or contaminants: _____________

Does the refrigerant identified agree with the manufacturer’s label or the retrofit label? Yes ___ No ___

CautionIf the type of refrigerant is incorrect or the refrigerant appears to be contaminated, consult your instructor before continuing.

5. Remove the refrigerant identifier from the system.

Troubleshoot the System 1. Attach manifold gauges or a refrigerant service center to the refrigeration system, Figure 6-2.

Describe the equipment used: ______________________________________________________

NoteIf the hoses do not have shutoff valves, purge the hoses by briefly cracking the hose fittings at the gauge manifold or service center inlet.


Figure 6-1. A popular make of refrigerant identifier is shown here.

Name ________________________________________________________


2. Check the refrigeration system’s static pressure.

Low side: _______________

High side: _______________

NoteIf the system shows no static pressure, consult your instructor before performing the next steps.

3. Start the engine and set the throttle to 1500 rpm.

4. Turn the air conditioning system on and set the controls to maximum cooling. Place the blower switch in its highest speed position.

5. Check that the compressor clutch engages and turns the compressor.

Does the compressor clutch engage? Yes ___ No ___

If Yes, go to step 7.

If No, go to step 6.

6. If the compressor clutch does not engage, check for electrical power at the clutch:

a. Set the air conditioner controls for maximum cooling.

b. Probe the clutch power connector with a non-powered test light or multimeter.

Is electrical power reaching the clutch? Yes ___ No ___

If Yes, the problem is in the clutch electromagnet. Make ohmmeter checks of the electromagnet to determine if the winding is open or shorted and ensure that the electromagnet is properly grounded.

If No, the control system is faulty or a wire is damaged or unplugged. Continue to the following substep.

Figure 6-2. Make connections to the refrigeration system carefully. Note the shutoff valves that prevent refrigerant loss.

Shutoffvalves


VII.D.2

VII.D.3


c. If power is not reaching the clutch, check the following clutch control components as applicable. The use of these devices varies between vehicles, so consult the appropriate service literature before proceeding.

• Compressor relay and control system.

• Low-pressure cycling switch.

• High-pressure cutout switch.

• Body computer.

• Thermal limiter (older vehicles only).

• Associated wiring.

NoteFor more information on the compressor clutch control system, see Job 9.

7. Install a temperature gauge in the outlet vent nearest the evaporator.

8. Check the refrigeration system’s operating pressure.

Low side: _______________

High side: _______________

CautionIf the cooling system fans are not operating, or if the high-side pressure exceeds 325 psi (2241 kPa), stop the performance test immediately and determine the cause.

How do the pressures compare to the specified pressures listed in step 2? Allow for ambient air temperature when deciding whether system pressures are correct. _________________________

If system pressures are not correct, what could be the cause? _____________________________

9. Check the air conditioning controls for the following conditions:

• Inoperative blower speeds.

• Inoperative temperature and/or mode controls.

• Temperature changes in response to controls.

• Temperature lowers sufficiently in A/C mode.

• Temperature rises sufficiently in heater mode.

• Interior airflow correct in all modes.

If any of the controls appear to be inoperative, consult your instructor and refer to Job 9.

10. Observe the refrigeration system to determine if other problems are occurring:

Is the evaporator icing? Yes ___ No ___

Is there any frost on the high side of the system (indicating a high side restriction)? Yes ___ No ___

Do you hear any unusual noises coming from the compressor? Yes ___ No ___

If Yes, describe the noises: ________________________________________________________


VII.A.6

VII.A.5

Name ________________________________________________________


NoteThe usual cause of odors is mold growing on the evaporator. Small animals sometimes crawl into the air ducts and die, and leaves occasionally build up in the cowl area and begin to rot. Other odors may be caused by a refrigerant leak in the evaporator or a heater core leaking coolant.

11. Check for system odors by performing the following steps:

a. Check under floor mats and seats to ensure the odor is not caused by another source in the passenger compartment.

b. Turn ignition switch on, then turn the air conditioner controls to the On position, and set the blower speed to high.

c. Note any odors.

•Is there an odor of oil, indicating an evaporator leak? Yes ___ No ___

•Is there an odor of coolant, indicating a heater core leak? Yes ___ No ___

•Is there a musty odor, indicating mold growing on the evaporator case? Yes ___ No ___

•Is there any other odor? Yes ___ No ___

If Yes, describe the odor: ______________________________________________________

What do you think is the source of the odor? _______________________________________

NoteConsult your instructor as to what steps to take to remove the odor. Possible solutions include spraying an anti-mold solution onto the evaporator, and removing duct work to remove odor sources, or cleaning the interior of the air conditioning system.

12. Place all air conditioner controls in the Off position.

13. Turn off the engine.

14. Remove gauges or service center hoses from the refrigeration system. Do not replace the service valve caps at this time.

Check for Refrigerant Leaks 1. Obtain a leak detector, Figure 6-3.

What type of detector are you working with? __________________________________________

WarningHalide (flame) leak detectors are not recommended. If you are using a halide leak detector, work in an open area and be extremely careful not to breathe the fumes. Make sure that the flame does not come into contact with flammable components or fuel vapors.


VII.D.8

VII.A.8


2. Set up and calibrate the leak detector as necessary.

Describe the calibration method: ___________________________________________________

3. Pass the leak detector probe around and under suspected leak areas while observing the detector face.

NoteThe most obvious places to begin looking for refrigerant leaks are wherever oil residue can be seen.

Were any leaks discovered? Yes ___ No ___

If Yes, where were the leaks located? _______________________________________________

4. Replace the service valve caps. From the observations made during this job, determine the refrigeration system problem.

Describe the problem: ____________________________________________________________

5. Consult your instructor and determine what service and repair steps should be taken.

List the needed service and/or repair steps here: _______________________________________

6. With your instructor’s permission take necessary service and/or repair steps.

List the service and repairs performed: ______________________________________________


Figure 6-3. A common make of leak detector is shown here.

Name ________________________________________________________


NoteRefer to other jobs in this project for repair and replacement procedures.

7. Recheck refrigeration system operation.

Is the problem corrected? Yes ___ No ___

If Yes, proceed to the next section.

If No, repeat the job as necessary.

Job Wrap-Up 1. Clean the work area and return tools and equipment to storage. Be sure to turn off the leak

detector before storing it.

2. Did you encounter any problems during this procedure? Yes ___ No ___

If Yes, describe the problems: ______________________________________________________

What did you do to correct the problems? ____________________________________________

3. Have your instructor check your work and sign this job sheet.

Performance Evaluation—Instructor Use Only

Did the student complete the job in the time allotted? Yes ___ No ___

If No, which steps were not completed?____________________

How would you rate this student’s overall performance on this job? ________________________

1–Excellent, 2–Good, 3–Satisfactory, 4–Unsatisfactory, 5–Poor

Comments: __________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

INSTRUCTOR’S SIGNATURE: _________________________________________________


project 2: job 6—diagnose an air conditioning system · pdf file... job 6—diagnose...

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