Five free practice questions on electrical system checks: content area C of the ASE T8 Preventive Maintenance Inspection (PMI) 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 technician must unplug a high-voltage cable connector on an electric truck to inspect its terminals. Any of these belongs in a safe set-up for that job EXCEPT:
- confirming the system is dead with a 12-volt test light.
- wearing insulated rubber gloves rated for the system voltage.
- checking for zero volts with a meter rated for that voltage.
- removing the key and keeping it away from the truck.
Show the answer
A. Correct. A 12-volt test light is not built or rated for high voltage and cannot prove a high-voltage circuit is dead; it could fail or arc in the technician's hand. Zero volts is confirmed with a meter of the right category rating, after the manufacturer's disable procedure and wait time.
Why not the others
B. Rubber insulating gloves of a class rated for the system's voltage, air tested before use, protect against shock and belong in the set-up. The test light step is the one that does not.
C. Verifying zero volts with a meter rated for the system voltage, after the disable procedure and wait time, is how the circuit is proved dead. A 12-volt test light cannot do that safely.
D. Removing the key and keeping it under the technician's control keeps anyone from powering the system back up during the job, so it belongs in the set-up. The step that does not belong is relying on a 12-volt test light.
ID T8-C-006 · Task T8-C-2 (ASE task list)
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A sealed flooded battery has a built-in hydrometer, a round indicator window in its top. What does the color shown in that window tell the inspector?
- Only the state of the cell it sits in
- The average charge of all six cells
- Whether the battery can crank under load
- Whether the charging voltage is correct
Show the answer
A. Correct. The indicator floats in the electrolyte of just one cell, so it shows that cell's charge and electrolyte level and nothing about the other five. The rested open-circuit voltage and a load or conductance test are what judge the whole battery.
Why not the others
B. The indicator sits in one cell's electrolyte only, so it cannot average the six cells; a weak cell elsewhere would not show. The battery's open-circuit voltage reflects all the cells together.
C. A green or dark window says nothing about cranking ability under load; it shows only one cell's charge. A load or conductance test checks cranking ability.
D. The indicator reports on the electrolyte of the cell it sits in, not on the charging system. Charging voltage is measured at the battery posts with the engine running.
ID T8-C-012 · Task T8-C-5 (ASE task list)
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A truck's starter has its own ground cable, so its mounting bolts carry no cranking current. At a PMI, two of its mounting bolts are found loose. What can this cause?
- Pinion misalignment that chips gear teeth
- Voltage loss in the cranking ground path
- Solenoid chatter from low pull-in voltage
- A starter that stays engaged after start
Show the answer
A. Correct. Loose bolts let the starter shift on its mounting, so the pinion meets the ring gear at an angle or the wrong depth; it grinds and chips teeth on both gears and can crack the mounting flange. The bolts are tightened to specification, and the pinion and ring gear are inspected for damage.
Why not the others
B. On this starter the ground cable, not the mounting, carries cranking current, so loose bolts do not add ground resistance. Their effect is mechanical: the pinion no longer meshes squarely with the ring gear.
C. Solenoid chatter comes from low voltage at the solenoid's control terminal or an open hold-in winding, not from the starter's mounting. Loose mounting bolts throw the pinion out of line with the ring gear.
D. A starter that stays engaged after the engine starts points to its control circuit or a sticking drive, not to loose mounting bolts. Loose bolts cause poor pinion-to-ring-gear mesh.
ID T8-C-017 · Task T8-C-7 (ASE task list)
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Why is a carbon pile connected across the batteries during an alternator's current output test?
- To check the batteries' cranking ability
- To keep the batteries from being overcharged
- To smooth the alternator's AC ripple
- To load the alternator to its full output
Show the answer
D. Correct. The truck's own loads and charged batteries rarely demand all the alternator can make, and the regulator cuts back the field once voltage reaches its setting. The carbon pile pulls voltage down so the regulator turns the field fully on and the alternator delivers its maximum, which is read with the amp clamp and compared with the maker's figure.
Why not the others
A. Loading a battery to judge its cranking ability is a separate battery load test. In the output test the pile draws current so that the alternator, not the battery, is pushed to its full output.
B. The pile adds load; it does not protect the batteries from overcharge, which is the regulator's job. It is there to pull voltage down so the alternator is driven to full output.
C. The pile is a resistive load and does not filter ripple; ripple is checked with a meter on AC volts. In the output test the pile draws enough current to make the alternator deliver its maximum.
ID T8-C-026 · Task T8-C-10 (ASE task list)
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At a PMI, a tractor has an inoperative rear clearance lamp that it is required to have, and an inoperative cab-mounted work lamp the owner added as an extra. Under 49 CFR 393.9, which must be capable of operating at all times?
- Neither until the annual inspection
- Both the clearance lamp and work lamp
- Only the required clearance lamp
- Only lamps used for night driving
Show the answer
C. Correct. The rule says every lamp the regulations require must be capable of being operated at all times, and it states that this does not extend to auxiliary or additional lamps. The clearance lamp is written up for repair; the added work lamp is noted for the owner.
Why not the others
A. Required lamps must be capable of being operated at all times, not just at a periodic inspection, so the clearance lamp is repaired now. The added work lamp is not covered by that requirement.
B. The rule specifically does not require an auxiliary or additional lamp, such as an added work lamp, to be capable of operating at all times. It applies to the required lamps, like the clearance lamp.
D. The requirement is at all times, day or night, for every required lamp. A required clearance lamp that does not work fails even on a daytime run; the added work lamp is not covered.
ID T8-C-030 · Task T8-C-12 (ASE task list) · 49 CFR 393.9
02Answer key
| Question | Answer |
|---|---|
| Q1 | A |
| Q2 | A |
| Q3 | A |
| Q4 | D |
| Q5 | C |
03What area C covers
On the electrical side, a PMI first identifies any high-voltage system on a hybrid or battery-electric truck and sets up to work near it safely. It then covers battery boxes, hold-downs, cables and battery tests, the starter and the cranking check, alternator mounting and output tests, interior and exterior lamps and reflectors, the trailer cord and receptacle, cameras and radar modules, and fuse panels and power distribution modules.
The ASE test specification calls this content area “Electrical/Electronics”. It carries 10 of the 50 scored questions, 20% of the test.
- Identify high-voltage parts and follow safe work practices
- Inspect battery boxes, covers, hold-downs and cable routing
- Record open-circuit voltage; load or conductance test batteries
- Inspect the starter and watch for slow or noisy cranking
- Inspect the alternator; test voltage, output and diodes
- Check interior and exterior lamps, reflectors and headlamp aim
- Test the trailer cord, receptacle and cord holder
- Check camera and radar mounts and power distribution modules
04What the questions turn on
What lies between the leads
A meter reads only what lies between its leads. On a post and its clamp during cranking, they span one joint, so a high reading means poor contact. Across the posts they include no cable, so cable drop is read from post to starter.
Open-circuit voltage needs a rested battery
Open-circuit voltage is read on a rested battery with nothing charging it. On a battery-electric truck that means switched off, because the DC/DC converter is charging the 12-volt battery whenever the truck is ready. A built-in hydrometer shows only the cell it sits in.
Load the alternator to test it
A carbon pile pulls voltage down so the regulator turns the field fully on and the alternator makes its maximum, read with an amp clamp. Diode ripple is read on AC volts under load, since a bad diode's ripple grows with current.
Required lamps and added lamps
Every lamp the federal rules require must be able to operate at all times and must not be hidden by dirt. A failed lamp the owner added is noted for the owner, and working fog lamps never stand in for a failed headlamp.
05The other content areas
The T8 test has five content areas. Each has its own page of free questions:
The ASE T8 Preventive Maintenance Inspection (PMI) 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.
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