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50 Cards in this Set

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

Can be a 1, 2, or 4 quadrent design.
What is the purpose of the auxiliary coolant pump (A31/m1)?
Assures uniform flow of coolant at low engine speeds.
operates only during heating demand.
What is the operating range of the refrigerant temp sensor (B12/1)?
- 40 to 212 degress F.
What does the multi-function sensor (B31/1)measure?
dew point
What must you do after replacing a stepper motor?
Normalize the stepper motor.