CHAPTER 8 Air-Conditioning System Components

CHAPTER 8

Air-Conditioning System Components

Automotive Heating and Air Conditioning, 6/eBy Thomas S. Birch

Copyright © 2012, 2010, 2006, 2001, 1997, 1991 Pearson EducationUpper Saddle River, NJ 07458 • All rights reserved.2

After studying Chapter 8, the reader will be able to:

1. Understand how the automotive A/C components operate.

2. Explain the variety of A/C components.

3. Explain the variety of A/C system controls.

OBJECTIVES



KEY TERMS• Barrier hose • Captive o-ring • Compression ratio • Condenser seals • Crankshaft • Damper drive • Discharge stroke • Displacement • Drive plate • Ester • Extruded tubes • Flux pole • Hang-on • Hygroscopic • Inline filters • Lip seal • Mineral oil • Modulator • Muffler • Outgassing • Polyalkylene glycol (PAG) • Polyol ester (POE) • Pressure relief valve

• Pulley • Reciprocating piston • Reed valves • Roof pack • Rotary compressor • Rotor • Scroll compressor • Seal cartridge • Seal seat • Short cycle • Sight glass • Stationary field • Suction stroke • Superheat • Thermal fuse • Thermistor • Transducer • Vane compressor



INTRODUCTION

• Automotive A/C components have been evolving steadily since the introduction of A/C in vehicles in 1940. • From the early days, when A/C was a very

expensive option in luxury cars, to today, when it is standard equipment in many models, many different types of systems have been used.



COMPRESSORS

• Most automotive compressors are of the reciprocating-piston type. • Compressors are steadily being downsized, made

smaller to fit into tighter locations to reduce the overall vehicle weight.• Rotary compressors • Vane and scroll compressors



COMPRESSORS



COMPRESSORS

• PISTON COMPRESSORS• INLINE PISTON COMPRESSORS• TWO-CYLINDER V COMPRESSOR• RADIAL COMPRESSORS• COAXIAL SWASH-PLATE COMPRESSORS• COAXIAL WOBBLE-PLATE COMPRESSORS• VARIABLE DISPLACEMENT WOBBLE-PLATE

COMPRESSORS• HYBRID VEHICLE COMPRESSORS



What Is a York Compressor?

• Most York compressors were made from aluminum with reinforcing webs on the cylinder head. The most common model numbers were in the DA 2 (die-cast aluminum, 2-cylinder) series. DA 2 is followed by two numbers that indicate displacement (for example, a DA 209 indicates a 9 cu. in. [147 cc] model). Displacement could also be determined by the shape of the end of the crankshaft. This compressor is currently used on heavy trucks, mobile industrial equipment, and farm equipment, and it is produced by Climate Control, Inc. A compact, 1-cylinder version of this compressor with a smaller overall size was manufactured.



What Is a Tecumseh Compressor?

• Tecumseh compressors were made from cast iron and were usually painted black. The most common model numbers were in the HG series. These letters were followed by three or four numbers that indicated displacement. Most of these compressors were HG 850 (for an 8.5 cu. in. [139 cc]) and HG 1000 (for a 10 cu. in. [164 cc]). An HG 500 model was also offered; it was a 5 cu. in. (82 cc) single-cylinder unit.



When Did GM Begin Using 5-Cylinder Compressors?

• In 1985, GM began installing a variable displacement compressor called the V-5 on certain vehicle models. This compressor is lightweight, at 12 lb (5.4 kg) (the 5-cylinder of the 1950s weighed 58 lb), and has a displacement of 0.6 to 9.2 cu. in. (10 to 151 cc).



SAFETY NOTE

• An electric compressor operates at a voltage of 42 to 230 volts, and these wires will have bright orange colored insulation. This is enough voltage to cause a severe to fatal shock. DO NOT TOUCH these wires without the proper protective equipment.



Honda Belt / HV dual Compressor



TECH TIP

• A technician becomes concerned with the compressor make and model when he or she needs to obtain a replacement for a failed compressor. Replacement compressors are available as new or rebuilt units, and proper identification is made from the vehicle make, model, and engine size. Then, if needed, proper identification is made by the old compressor make and model. At times, a failed compressor is replaced with a different compressor make and model if the mounting points, clutch diameter and belt position, and line fittings are the same.



COMPRESSORS

• COMPRESSOR CLUTCHES• DAMPER DRIVES

• COMPRESSOR SHAFT SEAL• COMPRESSOR LUBRICATION• COMPRESSOR SWITCHES AND RELIEF

VALVES



TECH TIP

• Damper drives cannot be cycled for evaporator temperature control. The compressor displacement control valve responds to electrical signals from the control module, and this controls evaporator temperature to deliver the desired outlet temperature and prevent evaporator freeze-up.



TECH TIP

• Damper drives cannot be turned off. The compressor operates whenever the engine runs. If the refrigerant is recovered or lost and the engine is started, compressor damage will result.



TECH TIP

• Mineral oil is miscible so it disappears into R-12. But, PAG oil is not miscible in R-134a; it tends to travel through the system in globs, being pushed by the refrigerant flow.



TECH TIP

• As little as 1% of PAG oil in an electric-compressor A/C system can cause an A/C system shutdown and possibly a vehicle shutdown.



TECH TIP

• It is important to keep oil containers closed so that the oil does not absorb water from the atmosphere. A mineral oil can absorb about 0.005% water by weight. A PAG or ester oil is very hygroscopic and can absorb about 2% to 6% water. Some synthetic oils undergo hydrolysis if exposed to too much water and revert back to their original components: acid and alcohol.



TECH TIP

• A relief valve discharging pressure produces a loud, popping noise, and the oil cloud that escapes with the refrigerant often looks like smoke. Most relief valves reclose after excess pressure has been released.



A/C Compressor Relief Valve

• AC Delco, Chevy, Ford



CONDENSERS

• The condenser has to get rid of the heat that is moved from the passenger compartment. • Automotive condensers are simple devices; older

tube-and-fin condensers are merely a tube bent back and forth into a serpentine shape with fins attached.

• After the tubes are pressed through the fins, return bends or manifolds are used to connect the tubes to give the desired flow pattern.



EXPANSION DEVICES

• THERMAL EXPANSION VALVES• ORIFICE TUBES• VARIABLE ORIFICE VALVES (VOVS)



What Is Inside a VIR?

• A TXV can also be a capsule inserted into a larger assembly. GM (between 1973 and 1975), Audi, and Volvo used a valves in receiver (VIR), a receiver– drier with the TXV and the suction throttling valves built into it. The TXV capsule was mounted so that it controlled the refrigerant flow from the receiver portion to the evaporator port.



TECH TIP

• In an operating system, the OT position can be located by finding the point where the liquid line changes temperature from hot to cold. If the system is not operating, the dimples in the line show the OT location.



EVAPORATORS

• An evaporator, like a condenser, is a simple heat exchanger device. • Some evaporators are merely groups of tubes with

fins attached. • Most evaporators are a series of plates sandwiched

together to form both the refrigerant and air passages.

• A plate-type evaporator is the most efficient of these two styles.



Why Do Some Evaporators Have a Third, Small Tube?

• Some evaporators have a third, very small line. This is an oil bleed line and is used in a system with a suction throttling valve (STV) . This line allows oil to be pulled from the bottom of the evaporator to ensure compressor lubrication when the STV is throttling. Many modern evaporators have a chemical coating to prevent bacterial growth that can cause bad odors.



What Are Some Evaporators Made from, Copper or Brass?

• Copper has antimicrobial properties that inhibit mold growth.



RECEIVER–DRIERS AND ACCUMULATORS

• Receiver–driers and accumulators serve two functions: • (1) They store a supply of liquid refrigerant• (2) they contain desiccant

• The purpose of refrigerant storage is to compensate for volume change due to temperature change or refrigerant loss.• Desiccant is needed to remove moisture or water,

which can cause rusting or corrosion.



RECEIVER–DRIERS AND ACCUMULATORS

• ACCUMULATORS• RECEIVER–DRIER• FILTERS AND MUFFLERS



TECH TIP

• The accumulator of some R-134a systems has an insulating jacket to help reduce the heat absorption and lower the air temperature at the discharge ducts.



TECH TIP

• The accumulator or receiver–drier is normally replaced if a system has been opened to the atmosphere for a period of time because the desiccant is probably saturated with moisture. It is also standard practice to replace the accumulator or receiver–drier whenever major service work is done on a system, especially if the compressor is replaced.



1974-1976

• Valves-In-Receiver (VIR) We can restore your GM Valves-in-Receiver (VIR). A VIR is a combination POA valve, drier and expansion valve all-in-one. Note that because it contains a drier, you should change the desiccant in it every time you open the system.



Valves-In-Receiver



Can a VIR Be Serviced?

• The VIR assembly is a serviceable unit: Almost every one of its individual components can be replaced. A kit that contains a desiccant bag, pickup tube filter, and O-rings is available.



TECH TIP

• When servicing a VIR, removal of the assembly is recommended to get better access to the screws, which tend to seize in the aluminum housing; also, index marks should be placed on the housing parts to ensure proper reassembly.



TECH TIP

• Service problems have occurred because scale and other debris from the condenser and compressor have plugged the OT. Normally if this happens the OT is cleaned or replaced. To prevent recurrence of this problem, a technician has a choice: thoroughly clean and flush out the system or install a filter. If the system is still working well, it can be much simpler and cheaper to add a filter than to flush the system.



HOSES AND LINES

• As mentioned earlier, because the suction and discharge lines in a system must be flexible, they are usually made of reinforced rubber hose. • The liquid line can be made from metal because the

parts it connects are rigidly mounted, but many systems use hose for this function also.

• Various end fittings of different sizes are used for the connections.• These fittings include female and male flare fittings;

female and male O-ring fittings; block, pad, or manifold fittings with O-rings; quick-connect or spring-lock fittings; and simple push-on hose-to-barb connections.



TECH TIP

• When making block connections, use a torque wrench. Overtightened connections damage the O-ring or distort the block and cause leaks.



ELECTRICAL SWITCHES AND EVAPORATOR TEMPERATURE CONTROLS

• Various electrical switches are used in A/C systems to prevent evaporator icing, protect the compressor, and control fan motors.

• SWITCHES AND RELAYS• SUCTION THROTTLING VALVES



TECH TIP

• If the system is low on refrigerant, it will short cycle , or rapidly cycle out and back in. This is the result of the compressor pulling the refrigerant out of the low side quickly to open either the cycling switch or the low-pressure switch. With the compressor off, the flow into the evaporator raises the pressure enough to reclose the switch and restart the compressor.



When Were STVs Commonly Used?

• Suction throttling valves have gone by different names, depending on manufacturer and year. Major models are as follows:• Robotrol: Early 1960s; aftermarket• Selectrol: Early 1960s; aftermarket• EPR: Chrysler Corporation, 1961 to 1979; mounted in compressor inlet• EPRV: Toyota and Lexus; mounted in suction line of ATC systems• ETR: Chrysler Corporation; mounted in compressor inlet• POA: GM, 1965 to 1975; mounted at the evaporator outlet• POA (capsule form): GM, 1973 to 1978 (Audi and Volvo); mounted in

the VIR• STV (early types): GM, 1962 to 1966; mounted at evaporator outlet;

allows driver control of temperature through mechanical cable or vacuum control

• STV (modern types): Ford Motor Company, 1972 to 1979; mounted at evaporator outlet or suction line

• STV (capsule): Ford Motor Company, 1976 to 1981; combined with TXV in a unit called the combination valve



Where Are STVs Located?

• In addition to electrical controls, some systems use a suction throttling valve (STV) to control evaporator pressure and prevent icing. An STV can be located anywhere between the evaporator tailpipe and the compressor inlet.



REAR A/C SYSTEMS

• Some larger vehicles (vans and small buses) have dual heat and A/C assemblies, with the rear unit mounted in a rear side panel or in the roof. • The rear A/C unit consists of an evaporator and

TXV that operates in parallel flow with the front unit.



AFTERMARKET A/C UNITS

• Aftermarket A/C units are installed in a vehicle after it is assembled and leaves the assembly line. • These units are designed for cars, trucks, vans,

recreational vehicles (RVs) and motor homes, ambulances, and tractors and farm equipment.



Vintage Air

• http://www.oldairproducts.com/catalog/1967-72-chevrolet-gmc-pickup/indash-louvers-c-1_31000000_120132056_31101000_120132104_120132105.html



SUMMARY

1. Various compressor types and models are used with mobile A/C systems.

2. Compressor models can use a variety of clutch, pulley, and port configurations.

3. Some variable displacement compressors use a damper pulley in place of a clutch.

4. Compressors are lubricated by oil that is circulated by the refrigerant.5. The major condenser types are round or flat tube and serpentine or

parallel flow.6. TXVs are used with receiver–driers that are located in the high side.7. Orifice tubes are used with accumulators that are used in the low side.8. Various line fitting types are used to connect the components.9. Various switches, sensors, and controls are used to control

compressor, blower, and fan operation.



Lab

• How to Connect gauges • http://www.youtube.com/watch?v=i9yv0euT7xA&fe

ature=related

• http://www.youtube.com/watch?v=XCELPgpnGjo&feature=related

• Performance Test• http://www.youtube.com/watch?v=uRbWx23Tgsw

CHAPTER 8 Air-Conditioning System Components

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