ASE 7 - Heating, Ventilation, and Air Conditioning. Module 8 Diagnosis, Testing & Repair

Transcription

1 ASE 7 - Heating, Ventilation, and Air Conditioning Module 8

2 Acknowledgements General Motors, the IAGMASEP Association Board of Directors, and Raytheon Professional Services, GM's training partner for GM's Service Technical College wish to thank all of the people who contributed to the GM ASEP/BSEP curriculum development project This project would not have been possible without the tireless efforts of many people. We acknowledge: The IAGMASEP Association members for agreeing to tackle this large project to create the curriculum for the GM ASEP/BSEP schools. The IAGMASEP Curriculum team for leading the members to a single vision and implementation. Direct contributors within Raytheon Professional Services for their support of translating a good idea into reality. Specifically, we thank: Chris Mason and Vince Williams, for their leadership, guidance, and support. Media and Graphics department under Mary McClain and in particular, Cheryl Squicciarini, Diana Pajewski, Lesley McCowey, Jeremy Pawelek, & Nancy DeSantis. For his help on the Heating, Ventilation, and Air Conditioning curriculum volume, Subject Matter Expert, Brad Fuhrman, for his wealth of knowledge. Finally, we wish to recognize the individual instructors and staffs of the GM ASEP/BSEP Colleges for their contribution for reformatting existing General Motors training material, adding critical technical content and the sharing of their expertise in the GM product. Separate committees worked on each of the eight curriculum areas. For the work on this volume, we thank the members of the Heating, Ventilation, and Air Conditioning committee: Steve Ash, Sinclair Community College Warren Farnell, Northhampton Community College Rick Frazier, Owens Community College Marvin Johnson, Brookhaven College Chris Peace, J. Sargeant Reynolds Community College Vince Williams, Raytheon

3 Contents Module 8 Acknowledgements... 2 Module Objectives... 4 Air Conditioning System Diagnosis... 6 Function Check... 7 System Performance Check... 8 Verify System Performance... 9 Pressure Zone Diagnostics... 1 Pressure Zone A...11 Pressure Zone B Pressure Zone C Pressure Zone D... 14

4 Objectives Upon successful completion of HVAC Module 8 Diagnosis, the ASEP student will be able to: Describe function test procedures Perform function check Explain Static Check procedures Perform Static Check procedures Explain System Performance Test Perform System Performance Diagnostic procedures NATEF Task Heating and Air Conditioning For every task in Heating and Air Conditioning, the following safety requirements must be strictly enforced: Comply with personal and environmental safety practices associated with clothing; eye protection; hand tools; power equipment; proper ventilation; and the handling, storage, and disposal of chemicals/materials in accordance with local, state, and federal safety and environmental regulations. VII. Heating and Air Conditioning A. A/C System Diagnosis and Repair 4. Performance test A/C system; diagnose A/C system malfunctions using principles of refrigeration. P-1. Diagnose abnormal operating noises in the A/C system; determine necessary action. P-2 6. Identify refrigerant type; conduct a performance test of the A/C system; determine necessary action. P-1 B. Refrigeration System Component Diagnosis and Repair 1. Compressor and Clutch 2. Diagnose A/C system conditions that cause the protection devices (pressure, thermal, and PCM) to interrupt system operation; determine necessary action. P-2 3. Evaporator, Condenser, and Related Components 4. Inspect A/C condenser for airflow restrictions; perform necessary action. P-1. Remove and reinstall receiver/drier or accumulator/drier; measure oil quantity; determine necessary action. P-1 6. Remove and install expansion valve or orifice (expansion) tube. P-2 7. Remove and reinstall evaporator; measure oil quantity; determine necessary action. P-3 8. Remove and reinstall condenser; measure oil quantity; determine necessary action. P-3 22 General Motors Corporation 8-4

5 C. Heating, Ventilation, and Engine Cooling Systems Diagnosis and Repair 1. Diagnose temperature control problems in the heater/ventilation system; determine necessary action. P-2 D. Operating Systems and Related Controls Diagnosis and Repair 1. Diagnose malfunctions in the electrical controls of heating, ventilation, and A/C (HVAC) systems; determine necessary action. P-2 4. Diagnose malfunctions in the vacuum and mechanical components and controls of the heating, ventilation, and A/C (HVAC) system; determine necessary action. P-2 STC Competencies A-7 Competencies for Advanced HVAC System Diagnostics 114.1W/H D. Diagnose an HVAC System concern using the ACR 2 1. Identify the system pressures 2. Compare system pressures to diagnostic tables 3. Identify the causes of abnormal system pressures using the pressure zone graph and diagnostic tables 4. Select the correct repair procedure in response to the pressure zone graph and diagnostic table 22 General Motors Corporation 8-

6 Air Conditioning System Diagnosis The technician will perform two diagnostic procedures when diagnosing customer concerns of insufficient cooling. These procedures are the Function Check and The System Performance Test. The function check provides the technician with three vital pieces of diagnostic information. This procedure checks the entire HVAC system for proper operation, verifies the customer concern, and provides additional related symptoms. It also helps to isolate the root cause to a particular sub-system. Technicians who fail to perform this check do not get an accurate picture of the overall system operation. Once the technician has performed the function check and determined there is insufficient cooling, it is time to isolate the concern to a subsystem. The system performance test is a function test of the refrigeration system. This test requires the technician to perform a preliminary check, measure ambient air temperature, stabilize the system, measure discharge air temperature, take manifold gauge readings, check compressor operation, and hand check the system. Depending on the symptoms found it might be necessary to perform a leak check. 22 General Motors Corporation 8-6

7 Function Check The functional test can be valuable at diagnosing the root cause of an air conditioning performance concern. By selecting various HVAC operating modes, desired temperatures, and fan setting at speeds, specific system responses should result. In doing so, the service technician can quickly determine if the air conditioning system's electrical, air delivery and refrigeration system are working properly. The following conditions indicate that the electrical circuits are functioning correctly: The air conditioning blower motor operates at the appropriate speed with the control (mode) in any position except OFF. Verify that the compressor clutch also engages. The blower motor will not operate in any speed with the control in the OFF position. The heater A/C control assembly (mode selector) is operating correctly when the designated outlets distribute air. The function check provides the technician with three vital pieces of diagnostic information. This procedure checks the entire HVAC system for proper operation, verifies the customer concern, and provides additional symptoms. It also helps to isolate the "root cause" to a particular sub-system. Technicians who fail to perform this check do not get an accurate picture of the overall system operation. 22 General Motors Corporation 8-7

8 System Performance Check A/C System Performance Test The ACR 2 is used to perform the A/C Performance Test. The A/C Performance Test measures the A/C system operating efficiency. Using the results of the A/C performance and the Pressure Zone diagnostics, you can isolate the cause of the customer concern. The procedure for the A/C System Performance Test is the same for all vehicles. However, the specified pressure and temperatures ranges differ depending on the vehicle. Static Pressure Check Before testing A/C system performance, your first step is to obtain static pressures reading. The purpose of the static pressure test is to determine weather or not there is enough refrigerant in the system to do an A/C System Performance Test. Figure 8-1, Compare the pressure reading to the target values to determine weather the refrigerant level is adequate. Different targets values are given for various ambient temperatures because the static pressure increases as ambient temperature increases. If the amount of refrigerant is adequate, the next step is to verify system performance 22 General Motors Corporation 8-8

9 Verify System Performance Record the following: ambient air temperature relative humidity outlet air temperatures low-side pressure high-side pressure Figure 8-2, Compare the readings to the A/C system performance table. If any of the readings are outside of the specified ranges, you should run the air conditioning for an additional minutes. Running the air conditioner longer, insures that the system has sufficient time to stabilize and allows for vehicle variations as well as high ambient temperatures. Reset the ACR 2 to obtain the new readings. 22 General Motors Corporation 8-9

10 Pressure Zone Diagnostics Once you have determined that system pressures or outlet temperatures are outside of their specified ranges, you must then determine the pressure zone in which the system readings fall. Using a zone classification graph, simply look at where the vehicle high and low pressures fall on the graph and you will know which zone to use. Keep in mine that these pressure values are vehicle specific. Therefore, you must consult the appropriate graph for the vehicle you are servicing. Figure 8-3, 22 General Motors Corporation 8-1

11 2 Pressure Zone A Definition: The high and low side pressures may be normal of slightly less than normal RETARD LOW HIGH Figure 8-4, Note: Outlet temp of 6 o F. Performance Conditions Low Side LO/Normal High Side LO/Normal Discharge air Insufficient cooling Possible Causes refrigerant under charge air delivery concern restriction refrigerant contamination 22 General Motors Corporation Figure 8-, 8-11

12 2 Pressure Zone B Definition: The low side pressure is higher than normal and the high side pressure is lower than normal RETARD LOW HIGH Figure 8-6, Note: Outlet temp of 7 o F. Performance Conditions Low Side HI High Side LO Discharge Air Insufficient cooling Possible Causes malfunctioning A/C compressor malfunctioning TXV Figure 8-7, 22 General Motors Corporation 8-12

13 2 Pressure Zone C Definition: The low and the high side pressures are both higher than normal RETARD LOW HIGH Figure 8-8, Note: Outlet temp of 7 o F. Performance Conditions Low Side HI High Side HI Discharge Air Insufficient cooling Possible Causes system overcharge restricted condenser air flow cooling fan malfunction engine cooling system malfunction Figure General Motors Corporation 8-13

14 2 Pressure Zone D Definition: The low side pressure is lower than normal and the high side pressure is higher than normal RETARD LOW HIGH Figure 8-1, Note: Outlet temp of 7 o F. Performance Conditions Low Side LO High Side HI Discharge Air Insufficient cooling Possible Cause restriction in the A/C system 22 General Motors Corporation Figure 8-11, 8-14