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ASE Automobile

A7 Heating & Air Conditioning — practice test

A7 is the Heating and Air Conditioning test, and it punishes guys who can only replace parts. It is a pressure-and-temperature diagnosis test wearing an HVAC costume, and the largest chunk of it is not refrigerant at all - it is the electrical and control side: blend doors, actuators, and automatic climate logic. Techs fail it because they know how to hook up gauges but never learned to read a gauge set against ambient temperature, and because they skip the recovery and handling rules they are legally working under every day.

Studying for A7 (Heating & Air Conditioning)? Overhaul Prep has 121 verified A7 questions written to the current task list — in the same formats the real exam uses (direct, Technician A/B, EXCEPT and most-likely-cause). Every answer comes with a written explanation, so you learn why instead of memorising a letter.

121A7 questions
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What's on the A7 test

Roughly 50 scored questions plus about 10 unscored pretest items you cannot pick out. Five task areas: A/C system diagnosis and repair (the biggest diagnostic block), refrigeration components split between compressor/clutch and evaporator/condenser, heating and ventilation with engine cooling, operating systems and related controls, and refrigerant recovery, recycling, and handling. The weight sits in two places: A/C system diagnosis, and operating systems and controls - which is mostly electrical, plus vacuum/mechanical and automatic climate control. Recovery and handling is a real block, not an afterthought.

High-yield A7 topics

The material that shows up year after year. If you're short on time, start here.

  • Gauge readings against ambient. Know the four patterns cold: both sides high (condenser airflow, overcharge, or non-condensables), both sides low (undercharge or restriction), low side high with high side low (compressor not pumping - worn reed valves or an internal leak), and low side low with frost at the orifice tube or TXV (restriction). They will hand you two pressures and an ambient temp and expect the cause. Also know static pressure roughly tracks the R-134a pressure/temperature chart at ambient - a system sitting at 70 psi at 70 F still has refrigerant in it.
  • Orifice tube/CCOT versus TXV systems. Which one has an accumulator (low side, after the evaporator) and which has a receiver-drier (high side, before the metering device). CCOT controls evaporator temp by cycling the clutch; TXV meters on superheat. A TXV stuck open floods the evaporator - high low-side, low superheat, slugging. Stuck closed starves it - low low-side, warm vent. This distinction drives half the diagnostic questions.
  • Variable-displacement compressors. Externally controlled units with a PWM control valve do not cycle the clutch in normal operation - the clutch stays engaged and displacement varies to hold evaporator temperature. A stuck control valve gives you full stroke (evaporator freeze-up, low side near vacuum) or minimum stroke (no cooling, low side high). Still know the basic clutch checks: air gap to spec, coil resistance in the 2-4 ohm range pulling roughly 3-5 amps.
  • Oil type and hybrid/electric compressors. PAG in a belt-driven system, but an electrically driven compressor on a hybrid or EV takes POE (ND-11 type), because PAG is hygroscopic and conductive - the wrong oil grounds the high-voltage motor windings and takes out the compressor and possibly the inverter. Pair it with the safety piece: de-energize the high-voltage system, never cut an orange cable. Easy question to miss, and they know it.
  • Recovery, evacuation, and charging procedure. Section 609 of the Clean Air Act covers motor vehicle A/C (not 608), certification is required, and venting is illegal. Identify the refrigerant before you recover - contaminated recovery ruins the tank and the machine. Recovery cylinders max at 80 percent by weight. Evacuate to 29-plus inHg and hold long enough to boil moisture out, then charge by weight, never by gauge. R-1234yf adds A2L flammability, unique fittings, SAE J2843 equipment, and an internal heat exchanger in the plumbing.
  • Heat, airflow, and blend control. No heat with good A/C is usually coolant side (low coolant, air pocket, stuck-open thermostat, plugged heater core with a cold outlet hose) or a stuck heater control valve, but on a modern box it is just as likely a blend-door actuator that lost its calibration. Clicking behind the dash means stripped actuator gears or a bound door, and most actuators must be recalibrated after replacement. A restricted cabin filter shows up as weak airflow and evaporator freeze-up.

Where techs lose points on A7

Good technicians miss these — not from lack of skill, but because the question is built to catch them.

  • High head pressure gets blamed on overcharge. On this test it is just as often restricted condenser airflow (fan clutch, debris, dead electric fan) or non-condensable gas from a system that was never evacuated right. If static or tank pressure sits well above what the pressure/temperature chart says for that ambient, you have air in it - recover and evacuate, do not bleed refrigerant out of the high side.
  • Low side high with high side low reads like an overcharge to a lot of guys. It is not. That is a compressor that is not pumping. A genuinely undercharged system pulls BOTH sides down. Do not let the words high and low side walk you into the look-alike answer.
  • A vacuum test is not a leak test. Pulling 29 inHg and holding it only proves the system is tight against about 14.7 psi, and small leaks seal up under vacuum and reopen at 250 psi. If an answer says the system held vacuum so there is no leak, that is bait - the right answer involves charging it and using an electronic detector or approved dye.
  • Assuming the clutch must cycle. On an externally controlled variable-displacement system, no cycling is normal, so no-cycle is not the fault. Same family of error: adding refrigerant by gauge pressure on a system specified to the ounce. The correct answer is almost always recover, evacuate, and charge by weight.

A study plan that works for A7

Roughly two weeks of real preparation, in the order that actually builds on itself.

  1. Days 1-4: Live in the pressure/temperature relationship. Learn the R-134a chart well enough to sanity-check static pressure at any ambient, then drill the four gauge patterns until you can name the cause without thinking. Sketch both system types - CCOT with accumulator, TXV with receiver-drier - and label high side, low side, and where a restriction shows up as frost.
  2. Days 5-8: Controls and electrical, because that is where the weight is. Clutch circuits, pressure switches and transducers, cycling and high-pressure cutouts, PWM control valves, blend/mode actuators and calibration, and automatic climate logic (in-car, ambient, sun load, evaporator temp sensors). Trace one real wiring diagram from A/C request to clutch engage and list every input that can block it.
  3. Days 9-11: Recovery, recycling, handling, plus heat and engine cooling. Section 609 rules, identify before recovery, 80 percent tank fill, evacuation targets, charge by weight, and the R-1234yf differences (A2L, fittings, J2843 machines, internal heat exchanger). Then the heat side: coolant flow, thermostats, heater core inlet/outlet temp checks, fan clutch and condenser airflow.
  4. Days 12-14: Practice tests only, and audit every miss. Write down WHY the wrong answer looked right - that is the actual A7 skill. Re-drill the compressor-not-pumping pattern, the non-condensable pattern, and the PAG/POE hybrid question until they are reflex.

Sample A7 questions

Straight from the bank — answers highlighted, with the explanation underneath.

In an automotive air-conditioning system, which component causes the refrigerant to change from a high-pressure vapor into a high-pressure liquid?

  1. Evaporator
  2. Condenser
  3. Compressor
  4. Orifice tube
WhyThe condenser rejects heat to the outside air, causing the high-pressure vapor leaving the compressor to condense into a high-pressure liquid. The evaporator does the opposite—it absorbs heat and boils low-pressure liquid into vapor.

Technician A says the condenser is part of the high-pressure side of the A/C system. Technician B says the evaporator is part of the high-pressure side. Who is correct?

  1. Technician A only
  2. Technician B only
  3. Both Technicians A and B
  4. Neither Technician
WhyThe condenser sits on the high side between the compressor and the metering device, so A is right; the evaporator is on the LOW side downstream of the metering device, so B is wrong.

A vehicle has an oily film that keeps forming on the inside of the windshield, a sweet odor in the cabin, and the coolant level slowly drops with no visible leaks under the vehicle. The technician should MOST likely suspect:

  1. A leaking heater core
  2. A clogged evaporator drain
  3. A leaking blower motor housing
  4. A thermostat stuck open
WhyA greasy fog on the glass plus a sweet (ethylene glycol) odor and unexplained coolant loss are the classic signs of an internally leaking heater core venting coolant into the HVAC case. A clogged evaporator drain produces clear, odorless water on the floor, not an oily sweet-smelling film.

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