The A7 covers heating and air conditioning: diagnosing A/C performance, refrigerant service and handling, system components, heating and engine cooling, and climate controls.
A lot of A7 questions give you gauge readings and ask what's wrong. Think about what the high side and low side should be doing, then figure out what's off.
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Question 1 of 15
Technician A says that when several HVAC components fail at once, each must have failed and be replaced. Technician B says an HVAC trouble code alone identifies the failed part, with no further testing needed. Who is correct?
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Answer: D. Neither A nor B
Several components failing together usually share a cause. Technician A is wrong. A trouble code names a circuit or condition, not a confirmed failed part; the code's diagnostic procedure finds the actual fault. Technician B is wrong too.
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Question 2 of 15
An electronic leak detector finds refrigerant escaping from the low-side service port's valve core, and the port's cap is missing. What should be done?
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Answer: B. Replace the core; install a cap
The valve core is replaced with one specified for that refrigerant, using a core tool (after recovery, unless the tool allows replacement under pressure), and a sealing cap is installed, since the cap is part of the port's seal.
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Question 3 of 15
Brown, oily sludge is found in the coolant reservoir. The engine has a coolant-cooled engine oil cooler. A combustion gas test on the coolant is negative. With the oil cooler pressure-tested off the engine, bubbles appear in the coolant passage. What is the most likely cause?
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Answer: B. A leaking engine oil cooler
Engine oil, at higher pressure than coolant, leaks through a failed oil cooler into the coolant. The negative combustion test and the cooler's failed pressure test point there. The cooler is replaced and the cooling system flushed of oil.
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Question 4 of 15
Technician A says flush solvent is pushed through the compressor and accumulator to clean them. Technician B says all solvent is cleared from flushed parts, as the flush equipment maker directs, before the system is reassembled. Who is correct?
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Answer: B. B only
The compressor, accumulator or receiver-drier and the orifice tube or expansion valve aren't flushed; they're removed or bypassed, and replaced or serviced as directed. Technician A is wrong. Leftover solvent contaminates the oil and refrigerant, so it's fully cleared before reassembly. Technician B is right.
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Question 5 of 15
Technician A says gauge pressures can be judged without knowing the ambient temperature. Technician B says that on many vehicles, the condenser fan runs whenever the compressor runs or the high side reaches a set pressure. Who is correct?
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Answer: B. B only
Normal operating pressures rise with ambient temperature and humidity, so readings are compared with the chart at the measured conditions. Technician A is wrong. Many systems run the condenser fan with the compressor, or when the high side reaches a set pressure, to control head pressure. Technician B is right.
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Question 6 of 15
An automatic climate control system can't hold the cabin at its set temperature, though the A/C and heater both work. All of these could cause it **EXCEPT**:
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Answer: D. A plugged evaporator drain
Automatic control depends on accurate inputs, like the in-car and sun load sensors, and on outputs that go where they're told, like a calibrated blend door. A plugged drain makes water overflow inside the case or onto the floor and can cause fogging or odor, but it doesn't affect temperature control.
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Question 7 of 15
Technician A says load-sensing compressor systems keep the compressor at full displacement at all times. Technician B says some systems compare compressor speed with engine speed and disengage the clutch if the compressor slows abnormally. Who is correct?
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Answer: B. B only
Load-sensing controls vary compressor output, or its engagement, with cooling demand and engine conditions. Technician A is wrong. Comparing compressor and engine speed detects a locking compressor or slipping belt, so the clutch can be released to protect the belt. Technician B is right.
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Question 8 of 15
An R-134a discharge hose is being replaced with a custom-made hose assembly. What kind of hose must be used?
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Answer: D. A barrier hose rated for the refrigerant
R-134a and R-1234yf molecules are small enough to permeate plain rubber, so A/C hoses have a nylon barrier liner. Replacement hose and crimped fittings must be rated for the refrigerant.
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Question 9 of 15
A cooling system is pressurized to its cap rating and loses pressure steadily, yet there are no external leaks, no coolant on the floor, and the oil looks normal. What is the best next test?
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Answer: B. Run a combustion gas test
With no external leak, coolant is leaving internally, into a cylinder or the oil. The oil looks normal, so a chemical block test (or exhaust gas analyzer) checks for combustion gases in the coolant, pointing to a head gasket or crack.
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Question 10 of 15
After A/C service on a hybrid with a high-voltage electric compressor, the vehicle sets a high-voltage isolation fault. The service machine injected PAG oil from a shared oil reservoir. Service information specifies an insulating POE oil. What is the most likely cause?
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Answer: C. PAG oil in the compressor
Electric compressors run their motor inside the refrigerant and oil, so they use an insulating oil, typically POE. PAG conducts more, lowering insulation resistance and setting an isolation fault. The oil is corrected as service information directs, using equipment or hoses kept free of PAG.
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Question 11 of 15
An evaporator leak is suspected. How is it checked with an electronic leak detector?
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Answer: B. Probe the drain outlet, blower off
With the blower off for several minutes, refrigerant from a leaking evaporator settles in the case. The probe is held at the drain outlet, or at a vent or blower opening as service information directs.
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Question 12 of 15
Airflow from the passenger floor outlet is very weak, while the driver's floor outlet and all other outlets work normally in every mode. In floor mode, air can be felt blowing out under the passenger side of the dash, above the outlet. What is the most likely cause?
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Answer: B. A disconnected floor duct
One outlet weak while its partner and the rest work points to that outlet's own path, and air escaping under the dash above it shows it's spilling out before it reaches the outlet. A floor duct off the heater case does exactly that. The duct is reconnected and secured.
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Question 13 of 15
The cooling fans run at high speed whenever the engine runs, even on a cold start. Scan data shows engine coolant temperature at -40°F, and an engine coolant temperature sensor circuit high code is stored. What is the most likely cause?
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Answer: C. A coolant sensor fail-safe
A -40°F reading and a circuit high code mean the sensor circuit is open, so the module can't tell engine temperature. As a fail-safe, it runs the fans at full speed to protect the engine. The sensor circuit is repaired, and the fans return to normal control.
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Question 14 of 15
On a cycling-clutch A/C system, airflow from the vents drops off after about 30 minutes of driving as the evaporator ices over. All of these could cause it **EXCEPT**:
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Answer: D. An inoperative condenser fan
An evaporator ices when it runs below freezing: freeze protection that doesn't stop the compressor in time, or too little warm air passing through it. A dead condenser fan raises high-side pressure and warms the whole system, so cooling gets worse; it doesn't ice the evaporator.
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Question 15 of 15
An engine overheats under load. The coolant is full, the thermostat opens, and the fans run. With the engine hot, an infrared scan of the radiator core shows the upper area hot but much of the lower area near ambient. What is the most likely cause?
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Answer: D. A restricted radiator
Hot coolant should heat the whole core, cooling gradually toward the outlet. Large cold areas mean coolant isn't flowing through those tubes, so they're clogged. The radiator is replaced and the source of the deposits addressed.
Want more? ASE Pro has 2,100+ practice questions with explanations.
If gauge reading questions slowed you down, practice matching high and low side readings to the common problems until it's quick.
Refrigerant handling questions are mostly rules, so they're easy points once you know them.
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