Climate control systems and air conditioning in automotive: Part 2

Continued part 1, part 2 of Climate control systems and air conditioning in automotive present the content: diagnostics and troubleshooting, initial vehicle inspection, pressure gauge readings and cycle testing; service and repair, refrigerant recovery, recycle and charging, servicing precautions, system flushing; the environment, global warming, the ozone layer; legislation, historical perspective, us perspective.
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Climate control systems and air conditioning in automotive: Part 24 Diagnostics and troubleshootingThe aim of this chapter is to:● Enable the reader to understand the range of techniques that can be used in diagnosing faults which affect system performance.4.1 Initial vehicle inspectionThe initial vehicle inspection is not a checklist. Information from the customer on the symp-toms, vehicle history and conditions upon which the fault occurs will allow the technician to beselective. The technician should first try to gather as much information as possible and assessif the symptom is normal behaviour (water dripping from underneath the vehicle) or not. Thetechnician should then assess if the environment in which the fault occurs can be replicated.For example, a fault which occurs when the vehicle has been idle for 2 days cannot be repli-cated the same afternoon the vehicle has been delivered. The correct conditions (temperature,load conditions) must be available to enable accurate fault detection. If conditions are notright then the customer must be aware that an initial diagnostic period will be allocated to thevehicle to carry out a range of tests allowing a number of possible causes to be verified. The technician should then ensure that they have access to all information required fromthe customer and for the vehicle. This includes fault finding charts, wiring diagrams, technicalservice data, diagnostic procedures, technical service bulletins etc. This information may be assimple as a radio code in case the power to the vehicle is interrupted to ensuring the customerhas access to a fault code pod (card) which allows access to any fault codes held within the sys-tem (see Chapter 3, sections 3.8, 3.9 and 3.10 for examples of information). Manufacturers alsohave software-based fault diagnostic procedures which direct the technician through guidedprocedures. Technical helplines are also available. Note – if the technician is inexperienced, then use the inspection as a checklist.Simple inspection routineCHECK CONDENSER FINS FOR BLOCKAGE OR DAMAGE● If the fins are clogged, wash them with water. Note – be careful not to damage the fins.CHECK THE POLLEN FILTER FOR SERVICE CONDITION● If dirty remove and replace. Diagnostics and troubleshooting 265MAKE SURE THAT DRIVE BELT IS INSTALLED CORRECTLY● Check that the drive belt fins fit properly in the ribbed grooves.CHECK DRIVE BELT TENSION● Check the drive belt tension.CHECK CONDENSER FAN FREELY ROTATES Note – after installing the drive belt, check that it fits properly in the ribbed grooves.CHECK ENGINE COOLANT LEVEL● Check coolant level. If unsatisfactory then test coolant system.START ENGINE AND TURN ON A/C SWITCH● Check that the A/C operates at each position of the blower switch. If blower does not oper- ate, check electrical circuits.CHECK MAGNETIC CLUTCH OPERATION● If magnetic clutch does not engage, check system pressure with gauges and power supply and operation of A/C control, e.g. electrical operation of low pressure switch.CHECK THAT IDLE INCREASES● When the magnetic clutch engages, engine rpm should increase.● Standard idle-up rpm: 900–1000 rpm.CHECK THAT CONDENSER FAN MOTOR CUTS INCHECK THAT THE HEATING PIPES LEADING TO THE HEAT EXCHANGERARE HOTCHECK THE PERFORMANCE OF THE A/C CONTROLS● Check the air distribution control, vary the direction of the air distribution and check air flow. Vary air temperature to test blend operation. Use a temperature probe to verify tem- perature range (4–60°C) and air direction (panel, floor, face).The initial vehicle inspection should direct the technician to one of the following:1. A performance diagnostic test on the A/C operation: ● A/C performance test. ● Pressure gauge analysis. ● Temperature measurement on A/C components. ● Refrigerant identification test. ● Level of refrigerant charge. ● Recovery. ● Leak testing – OFN, bubble, vacuum, UV dye. ● Recharge and retest.2. A/C electrical tests: ● Self-test checking for fault codes via control panel LCD/graphics display. ● Serial test using a handheld tester – wiggle test, actuator, DTC, data logger. ● In-depth ‘pin-by-pin’ electrical test using a break-out box or directly from the module connector.266 Automotive Air-conditioning and Climate Control Systems Note – systems with a fixed orifice valve and cycle switch (CCOT) are controlled mainly by pressure measurement. This means that pressure type tests like cycle tests are well suited to diagnosing system faults. Systems like TXV which are controlled by measuring temperature are well suited to all gauge and temperature tests.4.2 Temperature measurementsMeasuring the temperature at various points on the A/C system and making compar ...