Five free practice questions on batteries, starting and charging: content area G of the ASE T2 Diesel Engines test, 4 of its 55 scored questions (7.3%). 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 tractor's batteries are sealed absorbed glass mat (AGM) batteries with no removable vent caps. How is each battery's state of charge found?
- From a hydrometer reading of each cell's electrolyte
- From the voltage it holds under a half-CCA load
- From system voltage with the engine at fast idle
- From its rested open-circuit voltage reading
Show the answer
D. Correct. With the surface charge removed and nothing connected, a battery's open-circuit voltage tracks its state of charge, and the battery maker's chart converts the reading. On a sealed battery this replaces the hydrometer, and it tells whether to charge before a load test.
Why not the others
A. An AGM battery's electrolyte is held in glass-mat separators inside a sealed case, so there is no free liquid to draw into a hydrometer. Its state of charge is read from its rested open-circuit voltage.
B. A load test shows whether a charged battery can deliver current, not how charged it is; a discharged good battery and a failed charged one can both read low. The state of charge comes first, from rested open-circuit voltage.
C. With the engine running, system voltage is what the regulator is holding, so it says nothing about the batteries' own charge. State of charge is read from rested open-circuit voltage with the batteries disconnected.
ID T2-G-004 · Task T2-G-1 (ASE task list)
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A tractor with flat batteries is to be jump started with cables from another truck's 12-volt batteries. Why is the final clamp connected to a bare-metal engine ground away from the dead batteries rather than to their negative post?
- Its spark is then away from hydrogen at the batteries.
- It keeps the booster's current away from the truck's ECM.
- It routes the booster's current around the dead batteries.
- It protects the system if the cables are reversed.
Show the answer
A. Correct. Completing the circuit usually makes a spark, and batteries, especially deeply discharged ones being charged, give off hydrogen that a spark can ignite. Making the last connection at an engine ground away from the battery box keeps that spark clear of the gas.
Why not the others
B. The ECM is fed from the same system whichever ground the clamp is on, so the clamp's location does not shield it. The final clamp goes away from the batteries so its spark cannot reach hydrogen they may give off.
C. The dead batteries stay connected across the system, so booster current still reaches them wherever the last clamp goes. The reason for the remote ground is that the spark made by the last connection happens away from battery gas.
D. Where the final clamp goes does nothing for polarity: reversed cables would still connect the booster backward across the system. Polarity is checked before connecting; the remote ground keeps the final spark away from hydrogen gas.
ID T2-G-006 · Task T2-G-3 (ASE task list)
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White and green acid corrosion has built up on a truck's battery terminals and on the battery tops in its battery box. What is applied to neutralize the acid before the area is rinsed and the terminals are cleaned?
- A coat of dielectric grease or terminal protectant
- A solution of baking soda and water
- An aerosol electrical contact cleaner
- Distilled water from a squeeze bottle
Show the answer
B. Correct. Baking soda is a mild base that neutralizes sulfuric acid residue; it fizzes while acid remains. The solution is kept out of the cells through the vents, because inside it would neutralize electrolyte, and the area is rinsed afterward.
Why not the others
A. Grease or protectant is applied after the terminals are clean and tight, to keep moisture and acid off them. It seals over corrosion rather than neutralizing it; a baking soda and water solution does that.
C. Contact cleaner removes oil and light film from contacts but does not neutralize battery acid. A baking soda and water solution neutralizes the acid, after which the area is rinsed and the terminals cleaned.
D. Water rinses residue away but does not neutralize the acid, which keeps attacking metal. A baking soda and water solution neutralizes it first, then the area is rinsed.
ID T2-G-007 · Task T2-G-4 (ASE task list)
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In many heavy-duty cranking circuits, the key switch energizes a magnetic switch, and the magnetic switch's contacts feed the starter solenoid's windings. Why is the magnetic switch used?
- It holds the solenoid plunger in once the pull-in winding drops out.
- It cuts the circuit if the starter motor overheats while cranking.
- It keeps the solenoid's high current off the key switch.
- It carries cranking current from the batteries to the motor.
Show the answer
C. Correct. A heavy-duty starter solenoid's pull-in and hold-in windings draw a high current, more than the key switch and its long dash wiring can carry without burning contacts or losing voltage. The key switch drives only the magnetic switch's small coil, and its contacts feed the solenoid over short, heavier wires.
Why not the others
A. Holding the plunger and pinion in once the main contacts close is the job of the solenoid's hold-in winding. The magnetic switch is there because the solenoid's windings draw more current than the key switch can carry.
B. Where a starter has overheating protection, a thermostat in the motor opens the magnetic switch's circuit; the magnetic switch only relays the key's signal. It is used because the solenoid draws more current than the key switch can carry.
D. Cranking current passes through the solenoid's main contacts and heavy cables, never through the magnetic switch. The magnetic switch feeds only the solenoid's windings, whose current is too high for the key switch.
ID T2-G-008 · Task T2-G-5 (ASE task list)
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With the transmission in neutral and the key held in START, a truck's starter makes no sound and the engine does not crank. The batteries are fully charged, and the headlamps stay bright. Any of these could be the cause EXCEPT:
- an open coil in the starter's magnetic switch.
- a neutral-start switch that stays open in neutral.
- a broken wire from the key switch's START terminal.
- a drive clutch that slips on the armature shaft.
Show the answer
D. Correct. A slipping drive clutch can fail only after the solenoid has shifted the pinion and the motor is turning: the solenoid clunks and the motor whirs without turning the engine. A starter that makes no sound at all has a fault in the control circuit or the magnetic switch, ahead of the solenoid.
Why not the others
A. This could be the cause. With its coil open, the magnetic switch never closes, so no current reaches the solenoid and nothing at the starter moves or makes a sound.
B. This could be the cause. The neutral-start switch is in series with the magnetic switch's control circuit, so if it stays open nothing downstream is energized and the starter stays silent.
C. This could be the cause. A break in the START feed means the key switch's signal never reaches the magnetic switch, so neither the magnetic switch nor the solenoid acts and the starter makes no sound.
ID T2-G-009 · Task T2-G-5 (ASE task list)
02Answer key
| Question | Answer |
|---|---|
| Q1 | D |
| Q2 | A |
| Q3 | B |
| Q4 | C |
| Q5 | D |
03What area G covers
This content area covers the batteries, cranking and charging systems on trucks and tractors: identifying battery types and testing state of charge, load and capacity, charging batteries the right way, jump starting, cleaning and repairing batteries, cables and grounds, starters, relays, magnetic switches and solenoids, alternator output and remote sense circuits, and voltage drop tests on cranking and charging circuits.
The ASE test specification calls this content area “Starting and Charging System Diagnosis and Repair”. It carries 4 of the 55 scored questions, 7.3% of the test.
- Identify battery type and test state of charge
- Load test and capacity test batteries
- Charge batteries and jump start safely
- Clean and repair batteries, cables and grounds
- Test starters, relays, magnetic switches and solenoids
- Test alternator output and the remote sense circuit
- Run voltage drop tests on cranking and charging circuits
04What the questions turn on
Test each battery alone
A battery standing alone, with nothing connected, can lose charge only inside itself. One that falls to 10.5 volts while the others hold 12.6 has a cell contributing nothing, and in a parallel bank the good batteries drain into it.
Load test minimums and temperature
A cold battery delivers less voltage under load, so the battery maker's minimum for a load test drops with temperature. A reading is compared with the minimum for the battery's actual temperature, not with the figure for a warm battery.
Voltage drop needs current
Voltage drop equals current times resistance, so it is read with high current flowing. An ohmmeter can show 0 ohms on a cable that fails under load. A high drop on one side is then split across each cable, switch and stud.
Silence, clunk or chatter
A starter that makes no sound has a fault ahead of the solenoid, in the control circuit or magnetic switch; a slipping drive clutch clunks and whirs instead. A solenoid that chatters with good voltage at its terminals points to an open hold-in winding.
05The other content areas
The T2 test has eight content areas. Each has its own page of free questions:
The ASE T2 Diesel Engines 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, not affiliated with or endorsed by ASE (the National Institute for Automotive Service Excellence). Our questions are original, written from ASE’s published test specifications and task lists and other public sources. They are not actual ASE test questions and not recalled or “brain dump” questions. ASE is a trademark of its owner, and we never use the ASE logo. Standards and service information are cited, not reproduced.