Medium/Heavy Truck · Test T7 · Heating, Ventilation, and A/C
ASE T7 practice test: truck HVAC and A/C
T7 covers heating, ventilation and air conditioning on medium and heavy trucks: 50 questions (40 scored) in 60 minutes. Half of the scored questions are on the A/C system and its components. Passing it is not a refrigerant handling credential; the note below explains what is.
40 scoredquestions that count
60 mintesting time
20questions on the recert test
10practice questions here
What T7 covers
Checked Oct 23, 2026 against each source linked in the table. Content areas and scored questions from the spec table in the 2026 study guide, p. 38.
Question 1 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
A truck's temperature gauge reads higher than normal, but an infrared thermometer confirms the engine is at normal temperature. Technician A says a thermostat stuck partially open could be the cause. Technician B says a faulty coolant temperature sensor or its circuit could be the cause. Who is right?
Explanation
Incorrect: A thermostat stuck partly open makes the engine run cooler, which would make the gauge read low, not high; Technician A is wrong.
Correct: The engine is at normal temperature, so a gauge that reads high points to the sensor or its circuit giving a false reading; a partly open thermostat would read low.
Incorrect: Only Technician B is right; a thermostat stuck partly open makes the engine run cooler.
Incorrect: Technician B is right: a faulty coolant temperature sensor or circuit makes a false high reading.
Question 2 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
A truck's automatic temperature control does not hold the set temperature. The scan tool shows the in-cab temperature sensor reading −40 °F at all times. Which could be the cause?
Explanation
Incorrect: A climate control module is not the first suspect; an open sensor circuit is what produces a fixed −40 °F reading.
Incorrect: A signal shorted to ground reads very hot, not −40 °F.
Correct: A steady −40 °F is the reading a module defaults to when a thermistor circuit is open, so the system cannot control cab temperature.
Incorrect: A sticking blend door affects temperature, not the sensor's −40 °F reading.
Question 3 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
An air-operated HVAC mode door on a truck does not move when selected. Before testing the actuator itself, the technician should check the:
Explanation
Incorrect: Spring tension cannot be judged until the actuator is known to be getting air.
Incorrect: The actuator here is moved by air; its electrical control comes after the air supply is confirmed.
Incorrect: Software updates come after basic air and wiring checks.
Correct: An air-operated actuator cannot move without air, so the air supply pressure to its control valve is checked before the actuator is blamed.
Question 4 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
A truck's A/C condenser is being replaced. Which of these is the correct service sequence?
Explanation
Incorrect: Charging before evacuation leaves air and moisture in the system.
Correct: Refrigerant is recovered first, the condenser is replaced, the system is evacuated to remove air and moisture, and then it is charged.
Incorrect: Opening the system before recovery vents refrigerant.
Incorrect: Evacuating before recovery would release refrigerant into the air, which is illegal.
Question 5 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
Liquid refrigerant sprays from a disconnected service hose onto a technician's bare hand. The main hazard is:
Explanation
Correct: Liquid refrigerant boils off very fast at room temperature and pulls heat out of skin, causing frostbite.
Incorrect: Skin absorption is not the main risk; the freezing effect is.
Incorrect: Acid forms only with moisture over time in the system; it is not the danger of a liquid spray on skin.
Incorrect: Static shock is not a hazard of a refrigerant spray.
Question 6 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
Technician A says PAG refrigerant oil does not absorb moisture, so an opened container can be used months later. Technician B says mineral oil is the correct lubricant for R-134a compressors. Who is right?
Explanation
Incorrect: PAG oil absorbs moisture readily, so an opened container must be capped tightly and used soon; Technician A is wrong.
Incorrect: R-134a systems use PAG (or POE) oil; mineral oil does not mix with R-134a and will not circulate, so Technician B is wrong.
Incorrect: Both statements are false: PAG oil absorbs moisture, and mineral oil is not used with R-134a.
Correct: PAG oil absorbs moisture from the air, so an opened container does not keep, and R-134a compressors use PAG or POE oil, not mineral oil.
Question 7 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
When searching for a leak on truck A/C lines with an electronic leak detector, the probe should be moved:
Explanation
Incorrect: Six inches above the line is too far, and refrigerant sinks rather than rises.
Correct: Refrigerant is heavier than air and settles, so the probe is moved slowly, about 1 in. per second, just below each fitting and joint.
Incorrect: Fan airflow scatters the gas, and moving quickly misses small leaks.
Incorrect: Moving quickly can pass over a small leak, and the gas settles below a fitting, not above it.
Question 8 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
On a truck with a spring-engaged, air-released fan clutch, the fan runs engaged constantly, even with a cold engine. Which of these could be the cause?
Explanation
Incorrect: Worn friction lining makes the fan slip and turn too slowly, not stay engaged.
Incorrect: A sensor reading cold would tell the system to keep the fan released, not engaged.
Correct: On a spring-engaged, air-released fan clutch, air holds the fan off; losing that air supply lets the springs engage the fan all the time.
Incorrect: A stuck-open thermostat makes the engine run cool, which would keep the fan off, not on.
Question 9 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
Each time the A/C is switched on, a truck's clutch fuse blows. The clutch coil measures within its resistance specification. Which could be the cause?
Explanation
Incorrect: Too wide an air gap keeps the clutch from engaging, but it does not raise current and blow the fuse.
Correct: The diode across the clutch coil absorbs the voltage spike when the coil turns off; if it shorts, it connects power to ground and blows the fuse every time the clutch is energized.
Incorrect: A low charge makes the system cycle or not engage, but it does not blow the clutch fuse.
Incorrect: An open diode stops suppressing voltage spikes, but it does not draw current, so the fuse holds.
Question 10 of 10 · T7 Heating, Ventilation, and A/C · 40 itemsNot answered
On a truck's orifice tube system, the low side reads low, the high side slightly high, and the liquid line frosts right at the orifice tube location. The accumulator is warm. Which could be the cause?
Explanation
Incorrect: An overcharge raises both sides, and the low side would not be low.
Incorrect: A condenser fan that does not run raises high-side pressure, but the low side would be high too, with no frost at the orifice.
Incorrect: A low charge lowers both sides, and the high side would not be high.
Correct: Frost right at the orifice tube with a warm accumulator, low pressure on the low side and slightly high pressure on the high side points to a restriction at the tube itself.
Answer every question to see your score
Area by area
HVAC diagnosis, service & repair
6 scored questions: verifying the complaint, service information and codes, identifying the system and its refrigerant and oil, and performance checks that separate an A/C fault from a heating or control fault.
A/C system & components
The biggest area: 20 scored questions. Leak testing, recovery, recycling, evacuation and charging; refrigerant handling and checks for non-condensable gases; compressors and clutches, condensers, evaporators, hoses and expansion devices. Match the parts: an orifice tube system uses an accumulator, a thermal expansion valve (TXV) system a receiver-drier.
Heating & engine cooling
6 scored questions: heater cores and control valves, coolant condition and flow, thermostats, fans and fan clutches, because cab heat depends on the engine cooling system.
Operating systems & related controls
8 scored questions: blower motors and their controls, blend and mode doors, HVAC control modules and their inputs, A/C pressure switches and sensors.
T7 and EPA Section 609
Passing T7 does not meet EPA Section 609; ASE’s separate Refrigerant Recovery and Recycling Review and Quiz does. Under Section 609 of the Clean Air Act, anyone who repairs or services motor vehicle A/C for pay must be trained and certified through an EPA-approved program (EPA, read Oct 23, 2026).