ASE A7 flashcards
ASE A7 · Build recall with a focused review session.
32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Compressor function
- The compressor raises refrigerant pressure and temperature, moving heat from the evaporator to the condenser so the A/C system can reject heat outside.
- Condenser function
- The condenser receives high-pressure refrigerant vapor and transfers heat to outside air, causing the refrigerant to condense into liquid.
- Evaporator function
- The evaporator absorbs heat from cabin air as low-pressure liquid refrigerant boils into vapor inside the evaporator core.
- Expansion device function
- The expansion valve or orifice tube drops refrigerant pressure and controls flow into the evaporator, separating high-side and low-side pressures.
- Receiver-drier purpose
- A receiver-drier on TXV systems stores liquid refrigerant and removes moisture and debris before refrigerant reaches the expansion valve.
- Accumulator purpose
- An accumulator on orifice-tube systems stores excess liquid refrigerant and prevents liquid from entering the compressor.
- Superheat formula
- Superheat equals evaporator outlet temperature minus evaporator saturation temperature; it indicates how much vapor is above boiling point.
- Subcooling formula
- Subcooling equals condenser saturation temperature minus liquid-line temperature; it shows how far liquid refrigerant is below condensing temperature.
- Saturation pressure relationship
- For a specific refrigerant, saturation pressure corresponds to one saturation temperature; changing pressure changes boiling and condensing temperature.
- TXV operation
- A thermostatic expansion valve modulates refrigerant flow to maintain evaporator superheat, responding to evaporator outlet temperature and pressure.
- Orifice tube system control
- An orifice-tube system uses a fixed restriction and cycles the compressor clutch to control evaporator temperature and prevent freeze-up.
- PAG oil use
- PAG oil is specified for R-134a and R-1234yf automotive systems; it circulates with refrigerant and must match the system and refrigerant.
- Heater core operation
- The heater core transfers heat from engine coolant to cabin air; airflow through the core determines how much heat reaches the passenger compartment.
- Thermostat function
- The thermostat regulates coolant flow to the radiator, helping the engine reach and maintain proper operating temperature for heating and efficiency.
- Pressure cap function
- The radiator pressure cap raises the cooling system boiling point and releases pressure if it exceeds the specified cap rating.
- Coolant mixture purpose
- A coolant mixture provides freeze protection, boil-over protection, corrosion inhibition, and heat transfer; the ratio must match manufacturer specifications.
- Blend door function
- The blend door varies airflow through and around the heater core, controlling cabin air temperature in manual and automatic HVAC systems.
- Thermistor behavior
- A thermistor changes resistance with temperature; most automotive HVAC temperature sensors are negative temperature coefficient, so resistance drops as temperature rises.
- Blower resistor function
- A blower resistor adds resistance in series with the blower motor to provide lower fan speeds and reduce motor voltage.
- PWM blower controller
- A pulse-width-modulated blower controller varies motor speed by rapidly switching power on and off, avoiding the heat of a resistor.
- A/C pressure switch role
- An A/C pressure switch can disable the compressor clutch or control cooling fans based on refrigerant pressure to protect the system.
- Automatic climate inputs
- Automatic climate control uses ambient, interior, evaporator, sunload, and sometimes humidity sensors to adjust temperature, blower, and airflow mode.
- Section 609 certification
- Section 609 certification is required for technicians who service motor vehicle air-conditioning refrigerant; it covers refrigerant handling and venting prohibitions.
- Refrigerant recovery rule
- Refrigerant must be recovered from an A/C system before opening it; venting refrigerant to the atmosphere is prohibited.
- Refrigerant identification
- Identify refrigerant by system label or refrigerant analyzer before recovery; mixed or unknown refrigerant requires special handling and cannot be reused as specified.
- Evacuation purpose
- Evacuation removes air and moisture from a sealed A/C system; achieving and holding the specified vacuum verifies readiness and helps find leaks.
- Charge by weight
- Charging by weight uses a scale and the manufacturer-specified refrigerant amount; this is more accurate than charging only by gauge pressure.
- Performance test setup
- A performance test sets engine speed, blower speed, temperature controls, and cabin conditions as specified, then compares vent temperature and pressures.
- Low charge pressure sign
- Low refrigerant charge commonly shows low suction and low discharge pressures, along with weak cooling and possible compressor short-cycling.
- Poor condenser airflow sign
- Restricted condenser airflow or overcharge commonly raises high-side pressure and can increase low-side pressure, reducing cooling performance.
- Blower high-speed-only fault
- If the blower runs only on high speed, suspect an open blower resistor or faulty blower controller in the lower-speed circuit.
- No-heat diagnosis
- No cabin heat can result from low coolant, stuck-open thermostat, clogged heater core, failed blend door, or closed water valve.