ASE A7 Heating and Air Conditioning Cheat Sheet

HVAC and Engine Cooling Service, Diagnosis and Repair

42% of exam
Service and test conditions Refrigerant and lubricant selection Engine cooling and heating Performance verification

Refrigeration System Component Diagnosis and Repair

20% of exam
Compressors and protection Metering and heat exchangers Hoses, seals and drains Refrigerant-path integrity

Operating Systems and Related Controls Diagnosis and Repair

38% of exam
Blowers and drive circuits Doors and vacuum controls Sensors, networks and calibration Command versus response

Quick Facts

Exam ASE A7 Heating and A/C
Initial Test 60 total; 50 scored
Initial Time 75 minutes
Recertification 25 questions; 30 minutes
Official Domains 42% / 20% / 38%
Work Experience 2 years; approved training may count
Retake Wait 30 full days
Validity 5 years

Heat Requires Two Flows AC

Coolant carries heat; cabin air receives it.
Check coolant circulation Check door and airflow

Refrigerant Identity versus Appearance AC

Identification

Use appropriate refrigerant identifier
Confirm specified refrigerant before recovery

Appearance

Container colour is insufficient
Do not mix based on assumptions
Identify and segregate before service

Pressure Complaint Investigation AC

Gauge readings appear abnormal → Verify specified operating conditions
Condenser pressure excessive → Check airflow, charge and contamination
Suction low, cooling weak → Investigate charge, restrictions and airflow
Charge quantity uncertain → Recover and follow specified mass procedure
Repair complete → Recheck performance under complaint conditions

System Performance and Refrigerant Service AC

Test conditions Match OEM ambient/load settings
Pressure pattern Evidence, not a unique diagnosis
Refrigerant identity Identify before recovery
Charge quantity Use specified refrigerant mass
Evacuation Remove air/moisture; follow equipment procedure
Leak testing Use compatible approved detection method
Superheat Vapour temperature − local saturation temperature
Subcooling Local saturation temperature − liquid temperature
Temperature example 12°C−3°C=9K; example, not target

Identify Before Connecting AC

Identify refrigerant, equipment, lubricant and vehicle procedure.
Prevent contamination Preserve specified charge Verify repair under test conditions

Oil Family versus Approved Specification AC

Oil family

PAG or POE describes base chemistry
Does not prove compressor compatibility

Approved specification

Exact OEM oil and quantity
Preserves intended lubrication and insulation
Select by specification, not family alone

No-Heat Investigation AC

Engine warms unusually slowly → Check thermostat and temperature data
Engine temperature normal → Check coolant level and flow safely
Heater-flow evidence abnormal → Test valve, pump and restrictions
Heat source available → Check blend door and airflow
Service completed → Bleed as specified; verify cabin heat

Refrigerant and Lubricant Decisions AC

Section 609 Separate credential for compensated MVAC service
ASE A7 Does not confer Section 609 certification
Recovery equipment Use approved refrigerant-compatible equipment
Contaminated refrigerant Segregate; follow disposal/reclamation procedure
Compressor lubricant Exact OEM specification and quantity
Electric compressor oil Base family alone proves nothing

Coolant Flow versus Air Mixing AC

Coolant-side fault

Insufficient heat reaches heater core
Test valves, pumps and flow

Air-side fault

Heat source may be adequate
Test doors, ducts and airflow
Test both sides before replacement

Engine Cooling and Cabin Heating AC

Hot pressure cap Never open a hot pressurised system
Coolant selection Use approved chemistry and concentration
Pressure testing Stay within specified test pressure
Thermostat Compare warm-up with service specification
Fan and shutters Check command, movement and airflow
Coolant filling Use specified fill/bleed procedure

Heat Flow and Safe Service AC

Heater flow Check valves, pumps and restrictions
Hose temperature difference Not proof of a blocked core
Cabin airflow Inspect filter, ducts and outlets
Coolant corrosion Check chemistry, grounds and OEM tests
Electric heater/compressor Apply vehicle-specific HV safety procedure
Dashboard access Apply vehicle-specific SRS precautions

TXV Force Balance RE

Bulb opens; evaporator pressure and spring oppose.
Applies to mechanical TXV Electronic valves use commanded control

TXV versus Fixed Orifice RE

TXV

Modulates refrigerant flow
Commonly paired with receiver-drier

Fixed orifice

Opening does not modulate
Commonly paired with suction accumulator
Confirm the actual system design

Component Test Selection RE

Pulley rotates, cooling weak → Identify clutch or displacement control
Compressor debris discovered → Follow component contamination replacement guidance
Water enters cabin → Check evaporator drain and coolant clues
Refrigerant leak found → Repair compatible fittings and seals
Component replaced → Balance specified oil; leak-test system

Compression and Component Protection RE

Compressor function Raises vapour pressure; drives circulation
Variable displacement Compare command with pressure response
Clutch diagnosis Use specified gap and electrical tests
Drive coupling Inspect belt and breakaway coupling
Protection devices Test; never bypass safety protection
Oil balance Follow replacement-component oil procedure

Heat Exchangers and Metering RE

Condenser Rejects heat; check airflow and contamination
Evaporator Absorbs heat; check airflow and drain
Receiver-drier Commonly liquid/high side with TXV
Accumulator Commonly suction/low side with orifice
TXV Regulates evaporator-outlet superheat
Fixed orifice Fixed opening; inspect contamination/screens
Hoses and seals Use specified compatible parts

Command versus Response CO

Requested, supplied, commanded, moved: compare each link.
Scan data shows request Loaded tests verify delivery Feedback confirms response

Resistor versus Electronic Blower CO

Resistor control

Discrete resistance paths
High may bypass resistor network

Electronic control

Module varies motor output
Diagnose command and loaded circuits
Use the correct wiring diagram

Command versus Actual Response CO

Blower command changes only → Test loaded supply, ground and output
Actuator moves, temperature unchanged → Inspect door/linkage and heat source
Modes change under acceleration → Test vacuum reservoir and check valve
Sensor reading implausible → Check circuit and actual temperature
Module fails communication → Check power, grounds and network

Blower and Load-Circuit Tests CO

Voltage drop Measure while circuit carries load
Unloaded voltage May conceal a resistive connection
Resistor blower Check selected speed paths
Electronic blower Compare command and module output
Motor supply Check power and ground under load
Thermal protection Find cause before replacing failed protection
Command versus response Scan command does not prove movement

Open versus Ground-Short NTC CO

Open circuit

Specified pull-up circuit reads high
Check connector and continuity

Short to sensor ground

Specified pull-up circuit reads low
Check harness and sensor isolation
Confirm circuit before interpreting voltage

Actuators and Air Distribution CO

Blend door Controls air-mix temperature
Mode door Selects cabin outlet paths
Recirculation door Selects cabin or outside air
Mechanical cable Verify attachment and full travel
Actuator feedback Compare actual and commanded position
Door calibration Run specified relearn after applicable repairs
Duct leakage Air escapes before reaching outlet

Vacuum and Electrical Controls CO

Vacuum supply Check source under complaint conditions
Reservoir Stores vacuum during supply changes
Check valve Retains vacuum in intended direction
Vacuum actuator Check hose and diaphragm integrity
Clutch suppression diode Respect circuit polarity and protection
Fan control Compare command with loaded-circuit response
Control panel Verify inputs before replacing module

Sensors and Network Diagnosis CO

NTC sensor Resistance falls as temperature rises
Pull-up NTC circuit Open tends high; ground-short tends low
Temperature data Compare readings with actual conditions
Sunload input Adjusts comfort demand for solar heat
No communication Check power, grounds and network
Replacement module May need coding and calibration
Repair verification Reproduce complaint; check actual performance

Common Traps

Pressure Pattern

A clue needing further tests ≠ Unique proof of compressor failure

Electric Compressor Oil

Exact approved specification ≠ Any oil labelled POE is suitable

Vacuum Hold

One part of prescribed testing ≠ Proof of no pressure-side leak

Coolant Voltage

OEM diagnostic procedure and context ≠ One cutoff condemns every vehicle

Blower High Only

Verify actual resistor-circuit design ≠ Replace resistor in every system

HV and SRS Safety

Complete vehicle-specific disable procedures ≠ Low-voltage disconnect guarantees safety

Last Minute

1. 60 total; 50 scored; 75 minutes
2. Official domains: 42%, 20%, 38%
3. A7 does not grant Section 609
4. Identify refrigerant before recovery
5. Use specified charge mass and oil
6. Pressure patterns require corroboration
7. No universal evacuation time or target
8. Cool engine before opening cooling system
9. Match wiring diagram to blower design
10. Compare commanded and actual positions
11. Relearn modules and actuators as required
12. Verify repaired system under complaint conditions

ASE A7

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