Five free practice questions on HVAC and engine cooling service: content area A of the ASE A7 Heating & Air Conditioning test, 21 of its 50 scored questions (42%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
-
Before reading A/C line temperatures with an infrared thermometer, a technician wraps a strip of black electrical tape around each bare aluminum line and aims at the tape. Why?
- Tape shields the spot from moving air
- Bare metal gives off too little infrared
- The laser dot shows up better on tape
- The tape stops sweat from cooling the spot
Show the answer
B. Correct. Shiny aluminum emits little infrared and reflects heat from things around it, so an infrared reading on it is wrong; tape has a high, known emissivity, so its reading is close to the line's true temperature. A contact thermometer avoids the problem altogether.
Why not the others
A. A thin strip of tape does not insulate the line enough to matter. It is there to give the thermometer a surface that emits infrared the way the meter assumes.
C. The laser only shows where the meter is aimed; the reading comes from the infrared the surface gives off, which shiny metal emits poorly.
D. Condensation forms on a cold line whether or not tape is there, and it wets the tape too. The tape is there for its emissivity.
-
Before connecting a recovery machine to a vehicle with an unknown repair history, a technician checks the system with a sealant detection tool. Why?
- Sealant raises the system's static pressure
- Sealant makes an identifier read R-12
- Sealant must be flushed out before recovery
- Sealant can harden inside the machine
Show the answer
D. Correct. Most leak sealers react with air and moisture to harden, and drawn into a recovery machine they can solidify in its solenoids, filters and hoses. A system that tests positive is handled the way the machine's maker directs, for example with dedicated equipment, instead of being recovered into the shop's machine.
Why not the others
A. Sealant is an additive carried with the oil and does not change static pressure, which follows the refrigerant's temperature.
B. An identifier reads the refrigerant gases in its sample; sealant is a separate contaminant it is not built to measure, which is why a separate sealant test exists.
C. Nothing can be flushed while the system is still charged; the refrigerant comes out first. The sealant check decides how it is recovered.
-
A recovery/recycling/recharging machine's maker calls for a monthly check of its charging scale with a 10.00 lb test weight; the scale must read 9.95 to 10.05 lb, or it is recalibrated before more vehicles are charged. Today it reads 10.30 lb with the test weight. What should be done?
- Recalibrate the scale before charging
- Keep using it, since it is within 5 %
- Recalibrate it after today's charges
- Subtract 0.30 lb from each label charge
Show the answer
A. Correct. 10.30 lb is 0.25 lb above the 10.05 lb upper limit, so the scale is outside the maker's tolerance and every charge it weighs is suspect. It is recalibrated by the maker's procedure and rechecked with the test weight before the next charge.
Why not the others
B. The maker's tolerance is 9.95 to 10.05 lb, which is 0.5 %, not 5 %; at 10.30 lb the scale is out of tolerance.
C. The maker's rule is to recalibrate before more vehicles are charged; a scale reading 0.30 lb high on a 10 lb load makes every charge it weighs suspect, so waiting until the day's work is done puts wrong charges into those vehicles.
D. Taking 0.30 lb off every charge assumes a fixed error and would undercharge if the error is not fixed; the scale is recalibrated instead.
-
On many electric and plug-in hybrid vehicles, the A/C refrigerant circuit includes a chiller with its own expansion valve. What does the chiller do?
- It condenses refrigerant when the condenser fan is off.
- It cools the cabin air for the rear-seat outlets.
- It cools the high-voltage battery's coolant loop.
- It cools the engine coolant during hard acceleration.
Show the answer
C. Correct. The chiller is a refrigerant-to-coolant heat exchanger: refrigerant evaporating in it pulls heat out of the coolant that circulates through the high-voltage battery. That is why an A/C fault on these vehicles can limit battery cooling as well as cabin cooling.
Why not the others
A. Condensing rejects heat from the refrigerant; a chiller does the opposite, letting refrigerant evaporate and absorb heat. It absorbs that heat from the high-voltage battery's coolant loop.
B. Rear-seat cabin air is cooled by an evaporator in a rear HVAC case, which cools air, not coolant. The chiller transfers heat from the battery's coolant loop into the refrigerant.
D. Engine coolant is cooled by the radiator, not by the A/C system. The chiller's job is to pull heat out of the coolant loop that serves the high-voltage battery.
-
During an inspection, a heater hose is found soft, swollen and sticky along a 6 in. section in the middle of its run, directly below the valve cover, while the hose feels firm at both clamped ends. Which of these caused the damage?
- Electrochemical attack from inside
- Engine oil dripping onto the hose
- Heat from the engine running hot
- Pressure from a stuck radiator cap
Show the answer
B. Correct. Coolant hose rubber is not made to resist petroleum oil; oil dripping on it makes that section soft, swollen and sticky while the rest of the hose stays firm. The hose is replaced and the oil leak above it, here the valve cover gasket, is found and repaired so the new hose is not damaged the same way.
Why not the others
A. Electrochemical degradation starts inside the hose, usually within a few inches of the clamped ends, where the hose meets metal fittings. Here the ends are firm and the damage is in one section in the middle of the run.
C. Excess heat makes rubber hard and brittle, and it cracks rather than turning sticky. Soft, swollen rubber in one section under an oil leak points to oil.
D. Excess system pressure would stress the whole hose and swell its weakest point, but it would not make the rubber sticky. Soft, swollen, sticky rubber in one section below the valve cover is oil damage.
02Answer key
| Question | Answer |
|---|---|
| Q1 | B |
| Q2 | D |
| Q3 | A |
| Q4 | C |
| Q5 | B |
03What area A covers
This content area covers the A/C, heating and engine cooling work that starts most HVAC jobs: performance tests, reading pressures and temperatures, leak testing, identifying, recovering, recycling and charging refrigerant, evacuation and oil, service equipment and refrigerant handling rules, hybrid and electric vehicle A/C, heater and window fogging complaints, and cooling system tests, hoses, thermostats, pumps, fans and coolant.
The ASE test specification calls this content area “Heating, Ventilation, A/C (HVAC), and Engine Cooling System Service, Diagnosis, and Repair”. It carries 21 of the 50 scored questions, 42% of the test.
- Run performance tests and read pressures and temperatures
- Leak test with dye or an electronic detector
- Identify, recover, recycle, store and label refrigerant
- Evacuate, charge by weight and set oil quantity
- Check certified A/C service equipment
- Service A/C on hybrid and electric vehicles
- Diagnose heater output and window fogging problems
- Test and service cooling system parts and coolant
04What the questions turn on
Low-side pressure is a temperature
The low side holds boiling refrigerant, so its pressure sets the evaporator's boiling temperature. Each refrigerant has its own pressure-temperature table, so an R-1234yf reading is converted with an R-1234yf table, never the R-134a one.
A vacuum that rises, then levels
During a vacuum hold, a reading that climbs and then levels off is vapor, usually moisture, still boiling off inside the system. Air leaking in would keep the reading climbing toward atmospheric pressure. Moisture calls for more evacuation and another hold.
Recover it all, charge by weight
No gauge shows how much refrigerant is inside a system, so an overcharged or unknown system is fully recovered, evacuated and charged to the label weight. The recovered weight compared with the label shows how much had leaked away.
Testing the system and the cap
A cooling system pressure tester fits in place of the cap, so a falling gauge with no coolant visible outside points to an internal leak, not the cap. The cap is tested on its own adapter against the hold and open ratings.
05The other content areas
The A7 test has three content areas. Each has its own page of free questions:
The ASE A7 Heating & Air Conditioning practice test page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.
ToolboxPrep is an independent study site. It is not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original practice questions written to the published ASE test specifications; they are not actual test questions.