DENSO HVAC System for Recreational Vehicles Service Manual

Heating, Ventilation, and Air Conditioning System Service Manual for Recreational Vehicles This manual applies to vehicles using HFC-134a refrigerant ONLY.

i FOREWORD This manual was developed to assist certified technicians in servicing the air conditioning system on class A motorhomes built on Ford, GM, Spartan, or Freightliner chassis, equipped with a DENSO air conditioning system. Since the dash A/C system utilizes chassis components (compressor, condenser, receiver/drier and discharge hose), it is advised that the appropriate chassis repair manual for Ford, GM, or Freightliner be consulted when required or necessary.

iii TABLE OF CONTENTS GENERAL INFORMATION .................................................................................................. 1 1. The Purpose of Air Conditioning ................................................................................ 1 2. Technical Terms .......................................................................................................... 1 3. Change of State ......................................................................................................... 5 4. The Relationship Between Pressure and Temperature .............................................. 6 5. Basic Theory of Cooling ............................................................................................. 7 6. Refrigerant .................................................................................................................. 7 7. Principles of Air Conditioning ................................................................................... 10 8. Automotive Refrigeration System ............................................................................ 11 SAFETY PRECAUTIONS ................................................................................................... 14 1. Safety Precautions ................................................................................................... 14 2. Ultraviolet Rays and Ozone Layer ............................................................................ 15 TOOLS AND EQUIPMENT ................................................................................................ 16 1. Service Tool Kit ......................................................................................................... 16 2. Handling of Service Tools ......................................................................................... 16 3. Robinair Enviro Charge 34700 Series ...................................................................... 18 TORQUE AND BOLT SPECIFICATIONS ........................................................................... 19 1. Standard Torque: Coupling Nut Type Fittings ......................................................... 19 2. Torque Specification for Bolts/Nuts/Screws ............................................................ 19 COMPONENT LOCATIONS AND POSITIONS ................................................................. 20 1. Interior Component Locations (All Models) .............................................................. 20 2. Raised Floor Measurements and Cutouts ................................................................ 23 TROUBLESHOOTING ........................................................................................................ 24 1. Troubleshooting Table .............................................................................................. 24 2. Troubleshooting by Manifold Gauge ........................................................................ 25 3. Visual and Audible Troubleshooting Questions ........................................................ 33 4. Troubleshooting Chart .............................................................................................. 34 5. Insufficient Cooling ................................................................................................... 35 6. Abnormal Noise ........................................................................................................ 38 COMPONENT TESTING .................................................................................................... 39 1. Blower/Cooling Unit ................................................................................................. 39 2. Compressor Fitting ................................................................................................... 42 3. Refrigerant Hoses/Tubes .......................................................................................... 42 4. Heater Hoses: On Vehicle Inspection ....................................................................... 42 5. Heater ....................................................................................................................... 43 6. Thermostat ............................................................................................................... 45 7. A/C Control System: On Vehicle Inspection ............................................................. 46 8. Control Panel Removal ............................................................................................. 46 9. Pressure Switch ....................................................................................................... 47 10. Blower ...................................................................................................................... 48 11. Relays ...................................................................................................................... 49 12. Air Intake Servo ....................................................................................................... 50 13. Vent Mode Servo ..................................................................................................... 51

iv TABLE OF CONTENTS REFRIGERANT LINE REPLACEMENT ............................................................................. 52 1. On Vehicle Inspection ............................................................................................... 52 2. Refrigerant Lines Replacement ................................................................................ 52 3. Torque Specifications ............................................................................................... 52 4. CHASSIS .................................................................................................................. 53 REFRIGERANT CHARGING .............................................................................................. 63 1. About Certification ................................................................................................... 63 2. Section 609 of the Clean Air Act Amendments of 1990 .......................................... 64 3. Evacuating and Charging Refrigerant ...................................................................... 65 4. Refrigerant Volume ................................................................................................... 67 5. Performance Test ..................................................................................................... 68 WIRING DIAGRAMS .......................................................................................................... 70

1 GENERAL INFORMATION 1. The Purpose of Air Conditioning The purpose of an automotive air conditioner is to maintain a cool, comfortable environment for passengers. Here are the four ways this is achieved: • Temperature Control • Air Circulation Control • Humidity Control • Air Purification 2. Technical Terms A. Heat 1) Heat Quantity Heat is a form of energy. There are two units to measure heat quantity, Kcal or BTU (British Thermal Unit). • One Kcal heat quantity changes the temperature of one Kg of liquid water by one degree centigrade. • One BTU of heat changes the temperature of one pound of liquid water by one degree Fahrenheit. 1 Kcal = 0.252 BTU 1 BTU = 3.968 Kcal 2) Specific Heat Specific heat is the quantity of heat required to CHANGE THE TEMPERA- TURE of an object by one degree. The unit of specific heat is Kcal/kg°C or BTU/lb°F. 3) Heat Transfer As heat travels over a distance, it tends to lose energy. Heat can be transmitted through CONDUCTION, CONVECTION or RADIATION. It can also be transmitted by a combination of any or all of these methods. a) Conduction is the transfer of heat by direct contact. When you heat one side of a steel bar, the other side becomes warmer by conduction. b) Radiation is the transfer of heat by rays. Heat from the sun is transferred to the earth in rays. But the sun isn’t the only object that radiates heat. Every object that contains heat can radiate it. Fig. 1: The Four Factors of Air Conditioning Fig. 2: Heat Quantity Fig. 3: Specific Heat

2 GENERAL INFORMATION c) Convection is the transfer of heat by the movement of heated liquid or gas. When heat is applied to the bottom of a container of liquid or gas, the warmed particles at the bottom expand and rise. The colder particles at the top, which are denser than the heated particles, sink to the bottom. B. Temperature 1) Temperature Scales Temperature is the degree to which an object is hot or cold. The unit generally used to express this is degrees Centigrade (°C) or degrees Fahrenheit (°F). In the Centigrade scale, the freezing point (solid point) of pure water is taken as 0°C, and the distance between the freezing point and the boiling point are divided into 100 parts and each part is designated as 1°C. In the Fahrenheit scale, the freezing point of pure water is taken as 32°F, and the distance between the freezing point and the boiling point are divided into 180 parts with each part designated as 1°F. [°C] = 5/9([°F] - 32) [°F] = 9/5([°C] + 32) 2) Wet Bulb and Dry Bulb Thermometers The bulb (heat sensitizing part) of a glass tube thermometer is wrapped with a gauze or other rough mesh cloth. One end of the cloth is im- mersed in a water container to allow the water to be drawn up by a capil- lary action and to moisten the heat sensitizing part. The water in the cloth surface near the heat sensitizing part evaporates and robs the latent heat of evaporation from the surrounding air, causing the air temperature around the heat sensitizing parts to drop. The temperature registered by the thermometer at this time is called the wet bulb temperature. This is used to find out the humidity in combination with the dry bulb temperature. Fig. 4: Three Ways Heat is Transferred Fig. 5: Temperature Scales Fig. 6: Thermometer

3 GENERAL INFORMATION 3) Dew Point Temperature When the air surrounding us is cooled, the air temperature drops, and when the humidity becomes 100%, that is, when the dry bulb and wet bulb temperatures become the same, the water vapor contained in the air will be in a saturated state. On further cooling, the water vapor reaches a condition where it cannot remain in a vapor state so that a part condenses and becomes dew. The temperature at which the humidity becomes 100% and dew is formed is called the dew point temperature. C. Humidity 1) Humidity When you pour water and ice into a glass, you notice that drops of water are generated on the glass. Do you sometimes wonder where these drops of water come from? Drops of water come from the surrounding air, so humidity is water vapor contained in the air. 2) Relative Humidity There are two ways to measure humidity: relative humidity and absolute humidity. The most common way to measure humidity is using the relative method. Relative humidity is the amount of water the air contains, compared with the amount the air could hold at a given temperature. In other words, if the relative humidity is 50 percent, the air could hold as much water again as it does at that temperature. Water capacity means the amount of water vapor which the air could hold at a given temperature. The water capacity changes according to the temperature of the air. The water capacity of cooled air is lower. There- fore, the amount of vapor in the air at 50°C, 50 percent, is different from that in the air at 10°C, 50 percent. 3) Absolute Humidity Absolute humidity is the amount of water the air contains, compared with the dry air. D. Pressure 1) What Is Pressure? Pressure is defined as the vertical force exerted on a unit area by a solid, liquid, or gas. The unit generally used to indicate the pressure is “kg/cm”. When indicating blower performance, mmAq (water column) is generally used, and when indicating pressure below atmospheric (vacuum), cmHg (mercury column) is commonly used. When expressing boiler pressure, the atmospheric pressure is taken as the basis, and the pressure is expressed in number of atmospheres (atmos). The concept held toward pressure is entirely in accordance with Pascal’s law. Fig. 7: Humidity Fig. 8: Relative Humidity

4 GENERAL INFORMATION Pascal’s Law: “Pressure exerted on a liquid confined in a container is transmitted undiminished in all direc- tions. Regardless of container shape, if the interior area is equal, the pressure subject there will be equal.” 2) Atmospheric Pressure This is the pressure that is subjected on all objects and matter on earth. This pressure is the weight of the air surrounding everyone and is equal to 1 atmosphere. At this pressure the mercury column will be 760 mmHg (76 cmHg). 1 atm=1.03 kg/cm 2 =760 mmHg=14.7 psi Pressure gauges commonly indicate atmospheric pressure in units of kg/ cm 2 or psi. 3) Absolute Pressure Absolute pressure is that in which a perfect vacuum is taken as 0 kg/cm 2 . Thus, the atmospheric pressure, when expressed in terms of absolute pressure, will be 1.03 kg/cm 2 . To differentiate, pressure measured with a gauge is called gauge pressure. For identification, absolute pressure is indicated by [kg/cm 2 abs.] and gauge pressure by [kg/cm 2 G]. Absolute pressure to gauge pressure relationship is as follows: Absolute press. [kg/cm 2 abs.] + Gauge press. [kg/cm 2 G] + 1.03 kg/cm 2 4) Vacuum Vacuum is the pressure below atmospheric pressure and is expressed in terms of a mercury column (cmHg, mmHg). When the vacuum is measured with a mercury column, the difference between this measurement and that for atmospheric pressure becomes the amount of vacuum. Fig. 9: Pressure Fig. 10: Pressure Scales

5 GENERAL INFORMATION 3. Change of State A. State Change of Water Now, we will consider how ice changes its state when we add heat to it, because water is the most common example to understand heat and states of object. If we add heat to ice until the temperature of ice reaches 0°C (32°F), ice melts into water, and while the ice is melting, the temperature of ice and water remains at 0°C. After the ice has melted, the temperature of water begins to rise. When the temperature of water reaches 100°C (212°F), water begins to become steam. Until all the water becomes steam, the temperature of water remains 100°C (212°F). B. Sensible Heat and Latent Heat The chart below shows the relation between heat and temperature. There are two kinds of heat called sensible heat and latent heat. Sensible Heat can change the temperature of water but cannot change the state of water. Therefore, the sensible heat raises or lowers the temperature of water. In the case of water, 1 kg of water at 0°C must absorb 100 Kcal of sensible heat to change to 1 kg of water at 100°C. Latent Heat can change the state of water, but cannot change the temperature of water. Ice melts into water by adding latent heat and water evaporates into steam by adding latent heat. In the case of water, 1 kg of ice at 0°C must absorb 80 Kcal of latent heat to change to 1 kg of water at 0°, and 1 kg of water at 100°C must absorb 539 Kcal of latent heat to change to 1 kg of steam. C. The Three States of Matter As you know, matter exists in three states: solid, liquid and gas. In the case of water, the solid state is ice, the liquid state is water, and the gas state is steam. 1) Fusion When a solid melts into a liquid, heat is absorbed from its surroundings. 2) Solidification In the opposite situation, when liquid changes into a solid, heat is released to its surroundings. 3) Evaporation When liquid evaporates into gas, heat is absorbed from its surroundings. Fig. 11: State Change Of Water Fig. 12: Sensible Heat and Latent Heat Fig. 13: Three states of Matter

DENSO HVAC System for Recreational Vehicles Service Manual

You're Reading a Preview

Recently Viewed