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50 Cards in this Set
- Front
- Back
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How does the AC system cool the passenger compartment?
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An automotive AC system takes heat inside the passenger compartment and transfers it outside.
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What is used to transfer the heat?
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Heat is transfered using a refrigerant.
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What are the principles of refrigeration?
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Compression, Condensation, Expansion, Evaporation
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What is compression?
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When a low pressure gas gets compressed, it changes into a high pressure gas.
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What is condensation?
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When a high temp, high pressure gas losses heat,it condenses into a high temp, high pressure liquid.
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What is expansion?
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When a high temp high pressure liquid expands, it changes to a low temp, low pressure liquid.
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What is evaporation?
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When a low temp, low pressure liquid absorbs heat, it boils and changes from a liquid into a low pressure gas.
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What are the three laws of refridgeration?
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1-To refrigerate is to remove heat.
2-Heat flows to anything that has less heat. 3-If a change of state is to take place there must be a transfer of heat. |
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How does heat transfer?
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Heat always travels from hot to cold.
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What determines the rate at which heat transfers?
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The rate at which heat is transferred depends on how large the difference is between their temperatures.
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What is latent heat?
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Latent heat is the energy absorbed or released by a sustance during a change of state without a change in temperature.
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What are the basic parts of the automotive air conditioning system?
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1 Mechanical Compressor
2 Expansion valve 3 Two heat exchangers, the evaporator and condenser |
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What is the function of the compressor?
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1. The compressor pulls in low pressure low temp vapor and changes it to high pressure high temp vapor.
2. Moves the refrigerant. 3. Pressurises the system |
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What is the fuction of the condenser?
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The condenser exchanges heat to the outside air changing the high pressure vapor into a high pressure liquid.
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What is the function of the expantion valve?
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The expantion valve seperates the high pressure side from the low pressure side. Changes the high pressure high temp liquid to a low pressure low temp liquid.
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What is the function of the evaporator?
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The evaporator changes the low pressure liquid to a low pressure gas by absorbing the heat from the passenger compartment.
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What is the fuction of the reciever dryer?
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The receiver dryer removes moisture from the system.
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A cars cooling system removes how much of the engines heat?
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35%
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What are the characteristics of a variable compressor?
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1. Always Turns
2. No clutch 3. Has a wobble plate 4. Rubber coupling in case of seizur 5. Variable displacement & pumping capacity. |
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What are the characteristics of a condencer?
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1. Made of aluminum and receives high pressure vapor from the compressor.
2. Heat released to the environment is same heat absorbed by evaporator. 3. Upper 2/3rds contain hot refrigerant vapor, lower 1/3rd is warm liquid refrigerant. |
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How does the expantion valve work?
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As the evaporator temp outlet rises, the expansion valve opens and admits larger amounts of refrigerant.
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What three things does the evaporator do?
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1. Cools air
2. Dehumidifies air 3. Cleans air |
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When is a receiver/dryer used?
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Only on systems with expansion valves.
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What does AAC stand for?
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Automatic Air Conditioning
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What does C-AAC stand for?
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Convenience Automatic Air Conditioning
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C-AAC has what type of display?
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The C-AAC system has a digital display.
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AAC has how many fan speeds?
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AAC has twelve speeds.
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C-AAC has how many fan speeds?
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CAAC has seven settings
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What does "Thermatic" refer to?
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Thermatic refers to a two zone control module (N22)
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With the introduction of the W211, what was the EC (economy) button replaced with?
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The AC Off button replaced the EC (economy) button on the W211.
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How long does the rear defrost operate?
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Rear defrost operates for 6 - 17 minutes depending on outside temp, in car temp, and vehicle speed.
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What does "Thermotronic" refer to?
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Thermotronic refers to a four zone control module (N22/7)
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What does Activated Charcoal Filtration (ACF) do?
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Absorbs odors
Cannot be cleaned, replace as a unit. |
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What do the dust filters do?
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Filter fresh and recirculated air. Cannot be cleaned.
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Which model has "B" pillar ventilation?
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W211, four zone only.
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Can the optional rear ac on the W220 be controlled from the front?
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Yes, can be controlled from the front pushbutton control module (N22)
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How is window fogging avoided while maintaining in-car temp level?
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Blower speed is increased by maximum 15% in low ambient temps of -10 to - 15 degress C
(-15 to 5 degress F) |
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Why does the blower regulator (A32n1) require less heat sinking?
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The blower regulator (A32n1) has transisterized circuitry.
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Where is the blower regulator (A32n1) located?
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The blower regulator (A32n1) is located in the blower housing.
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How is the blower speed increased or decreased?
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By adjusting the Pulsed Width Modulation, Longer PWM, faster blower speeds.
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Where are the In Car Temp Sensors (N70b1)located on the W220?
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1. Top right of the passenger side control button
2. Overhead control module |
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Where are the In Car Temp Sensors (N70b1)located on the W203?
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1. Top left of the passenger side control button. CAAC
2. Center of push button control module. AAC 3. Overhead control module |
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Where are the In Car Temp Sensors (N70b1)located on the W211?
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1. Located behind steering wheel on dash.
2. Overhead control module. |
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What type of sensor is the "In car temp sensor" (N70b1)?
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NTC, high temp low resistance and low temp high resistance.
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What does the ambient temp sensor (B14)do?
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Monitors outside temp.
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What does the sun sensor (B32/2) measure?
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The intesity and the direction of the sunlight.
Can be a 1, 2, or 4 quadrent design. |
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What is the purpose of the auxiliary coolant pump (A31/m1)?
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Assures uniform flow of coolant at low engine speeds.
operates only during heating demand. |
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What is the operating range of the refrigerant temp sensor (B12/1)?
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- 40 to 212 degress F.
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What does the multi-function sensor (B31/1)measure?
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CO NOx
dew point temp |
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What must you do after replacing a stepper motor?
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Normalize the stepper motor.
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