Five free practice questions on A/C refrigeration components: content area B of the ASE A7 Heating & Air Conditioning test, 10 of its 50 scored questions (20%). They are in the ASE format: four options, one best answer. Answer each one before opening the explanation. No account, no email.
01The questions
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A new multi-rib belt is being installed on an engine whose A/C compressor belt is held by a spring-loaded automatic tensioner. How is the belt tension set?
- By turning an adjuster bolt on the tensioner
- By shifting the compressor in a slotted mount
- With a tension gauge, then by locking the arm
- By letting the arm down onto the belt
Show the answer
D. Correct. A spring-loaded tensioner applies its designed force by itself: the arm is levered back, the belt is routed, and the arm is let down onto it, with nothing to adjust or lock. The wear indicator is then checked against its marks.
Why not the others
A. A spring-loaded tensioner has no adjuster; adjuster bolts belong to manual tensioners and fixed idler or bracket designs. Its spring sets the tension once the arm is let down onto the belt.
B. Slotted compressor mounts are used on engines without an automatic tensioner. With a spring-loaded tensioner, the spring sets the tension once the arm is let down onto the belt.
C. A spring-loaded tensioner's arm is not locked; it must stay free so the tension stays constant as the belt and load change. The spring sets the tension by itself.
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Why is mineral oil not used as the compressor lubricant in an R-134a system?
- It absorbs more moisture than PAG oil
- It reacts with R-134a to form acids
- It does not mix well with R-134a
- It is too thin to protect the compressor
Show the answer
C. Correct. R-134a and mineral oil do not mix well, so oil that leaves the compressor tends to collect in the evaporator and lines instead of being carried back, starving the compressor and coating the heat exchangers. R-134a systems use the PAG or POE oil the manufacturer specifies.
Why not the others
A. Mineral oil absorbs far less moisture than PAG oil, so moisture is not the reason it is avoided. It is not used because it does not mix well with R-134a and so does not return to the compressor.
B. Mineral oil and R-134a do not react to form acids; the problem is that they do not mix well, so the oil is not carried back to the compressor. Acids in a system come mainly from moisture.
D. Mineral oils come in a range of viscosities, so thickness is not the issue. The problem is that mineral oil does not mix well with R-134a and is not carried back to the compressor.
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A replacement receiver/drier has its inlet and outlet marked. Why must it not be installed backward?
- Its desiccant would stop absorbing any moisture
- Its outlet would draw vapor in place of liquid
- Its switch port would end up on the low side
- It would raise the pressure on the low side
Show the answer
B. Correct. A receiver/drier's outlet connects to a pickup tube that draws liquid from the bottom, where the liquid collects; reversed, the refrigerant would leave from the top, where vapor gathers, and the expansion valve would be fed vapor and bubbles instead of solid liquid. Cooling suffers even with a full charge.
Why not the others
A. The desiccant absorbs moisture from the refrigerant flowing past it in either direction. The marking matters because the outlet pickup tube must draw liquid from the bottom of the receiver.
C. The whole receiver/drier sits on the high side between the condenser and the expansion valve, so reversing it cannot put any of its ports on the low side. The problem is that the outlet would draw vapor from the top instead of liquid from the bottom.
D. The receiver/drier is entirely on the high side, and a reversed one feeds the expansion valve vapor rather than liquid, which does not raise low-side pressure. Direction matters so the outlet draws liquid from the bottom.
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After a compressor failure spread debris through an orifice-tube system, the manufacturer's procedure adds an in-line filter to stop debris still in the high side from reaching the metering device. Where does the filter go?
- In the liquid line ahead of the orifice tube
- In the discharge line ahead of the condenser
- In the suction line ahead of the compressor
- In the line between orifice tube and evaporator
Show the answer
A. Correct. Debris left in the condenser and liquid line travels with the liquid toward the metering device, so a filter in the liquid line just upstream of the orifice tube catches it before it can plug the tube. Some filters of this kind have an orifice built in, in which case the old tube comes out.
Why not the others
B. A filter between the compressor and condenser is upstream of the condenser, so it cannot catch debris already lodged in the condenser. The filter goes in the liquid line, after the condenser and ahead of the orifice tube.
C. A suction-line filter sits on the low side, after the metering device, so debris from the high side would reach the orifice tube first. The filter goes in the liquid line ahead of the tube.
D. A filter after the orifice tube is too late: debris from the high side would already have reached and plugged the tube. It goes in the liquid line ahead of the orifice tube.
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An orifice tube has no moving parts. Which of these sets how much refrigerant flows through it?
- Low-side pressure acting on a diaphragm
- The temperature at the evaporator outlet
- A signal from the A/C control module
- The pressure difference across the tube
Show the answer
D. Correct. A fixed orifice passes more refrigerant as the difference between high-side and low-side pressure grows, and the condition of the liquid reaching it also affects the flow. Because it cannot adjust to load, an orifice-tube system relies on the accumulator to hold whatever liquid the evaporator does not boil off.
Why not the others
A. A diaphragm moved by pressure needs moving parts, which an orifice tube does not have. Its flow follows the pressure difference between the high and low sides.
B. Sensing the evaporator outlet temperature is what a TXV's bulb does. An orifice tube has nothing to sense with; its flow follows the pressure difference across it.
C. Module control belongs to an electronic expansion valve. An orifice tube is a fixed passage whose flow follows the pressure difference across it.
02Answer key
| Question | Answer |
|---|---|
| Q1 | D |
| Q2 | C |
| Q3 | B |
| Q4 | A |
| Q5 | D |
03What area B covers
This content area covers the parts the refrigerant passes through and the devices that protect them: compressors, clutches and displacement controls, belts and tensioners, refrigerant oil, hoses, lines, fittings and mufflers, condensers and evaporators and the air through them, receiver/driers and accumulators, expansion valves and orifice tubes, service valves, relief valves and internal heat exchangers.
The ASE test specification calls this content area “Refrigeration System Component Diagnosis and Repair”. It carries 10 of the 50 scored questions, 20% of the test.
- Diagnose pressure, thermal and electronic protection cutouts
- Service compressor belts, clutches and breakaway hubs
- Check compressor oil type and quantity
- Test variable displacement compressor controls
- Service hoses, lines, fittings, seals and mufflers
- Check condenser and evaporator airflow, seals and drains
- Replace driers, accumulators, expansion valves and orifice tubes
- Inspect service valves, relief valves and heat exchangers
04What the questions turn on
Short cycling on the low side
With a cycling switch on the low side, both a low charge and a plugged orifice screen make the clutch short-cycle. A low charge also holds the high side low. A plugged screen leaves the high side in range and frosts the line past it.
Superheat shows the valve's feed
Superheat is the evaporator outlet temperature minus the boiling point at low-side pressure. Superheat well above specification with a correct charge means the expansion valve is feeding too little. A sensing bulb that works loose does the opposite and floods the evaporator.
When the high side runs high
High-side pressure that is high at idle but in range at highway speed points to airflow at low speed, such as missing condenser seals and air dams. High at every speed, with good fans and charge, points to debris packed between condenser and radiator.
Oil goes where refrigerant goes
Refrigerant oil travels with the refrigerant and collects throughout the system, so the oil drained from an old compressor is only part of the total. R-134a systems use the PAG or POE oil specified, because mineral oil does not mix well with R-134a.
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.