Heavy Duty Technician – Prep Test #2 (Engine Systems & Diagnostics Practice
Exam)
Which of the following tests would be most efficient in identifying a high resistance in a starting
circuit?
(A) Disconnect battery, perform resistance test with an ohmmeter.
(B) Install ammeter, Perform a current draw test.
(C) Check the chassis data bus for fault codes
(D) Voltage drop test the circuit while cranking. - correct answer ✔✔(D) Voltage drop test the
circuit while cranking
When testing the specific gravity of the cells in a fully charged battery, one cell reads 1.220
while the others all read between 1.265 and 1.270. What should be done to the battery? -
correct answer ✔✔(B) Replace the battery
When testing alternator components, an ohmmeter reads 1 ohm between the rotor slip rings
and the rotor shaft. Which of the following is indicated?
(A) Reading is within specification
(B) Rotor windings are shortened to each other
(C) Rotor windings are shorted to ground
(D) Rotor windings are open - correct answer ✔✔(C) Rotor windings are shorted to ground
A heavy duty truck has no crank condition. Which of the following steps should be performed
first?
(A) Start grunt connection
(B) Start control circuit
(C) Starter solenoid
(D) Battery state of charge - correct answer ✔✔(D) Batter state of charge
,In order to test voltage drop through a starter circuit magnetic switch, which of the following
must be done?
(A) Remove the magnetic switch from the cranking circuit.
(B) Disconnect the starter solenoid to start strap
(C) Energize the control circuit
(D) Short through the magnetic switch load terminals - correct answer ✔✔(C) Energize the
control Circuit
If a truck alternator is full fielded in operation, which of the following will be the most likely
result?
(A) Maximum charging system current
(B) Batteries discharge rapidly
(C) Dim Lights
(D) Circuit breakers trip - correct answer ✔✔(A) Maximum charging system current
An alternator is carbon pile tested and has zero output. Which of the following is the most likely
cause?
(A) Battery is only 25% charged
(B) Truck and trailer electrical load exceeds alternator specifications
(C) Open alternator field circuit
(D) Loose drive belts - correct answer ✔✔(C) Open alternator field circuit
A fully charged batter is to be tested in a shop where the ambient temperature is above 21
degrees celsius. The state of charge test indicates 12.6 volts and when a carbon pile is used to
load the battery for the 15-second load test, the voltage bottoms at 9.3 volts. What should be
done? - correct answer ✔✔Replace the battery
, When branch testing a starter motor, the amperage draw exceeds the manufactures
specifications. Which of the following is the most likely cause?
(A) Shorted motor windings
(B) Burned solenoid contacts
(C) Open motor windings
(D) Insufficient brush spring tension - correct answer ✔✔(A) Shorted motor windings
The left turn lights on a tractor/trailer combination function on the tractor but not the trailer.
When checking the 7-pin trailer connector, which colour code assignment should be checked
first? - correct answer ✔✔(B) Yellow
A technician is measuring voltage drop across a triple cluster of three marker lights. Each is
tested by placing one voltmeter probe on the positive terminal and the other on the unit
ground terminal. Each of the three readings is almost identical. Which of the following readings
would suggest that the circuit is in good condition?
(A) 0.15 volts
(B) 0.80 volts
(C) 4 volts
(D) 12 volts - correct answer ✔✔((D) 12 volts
A headlight unit terminal feels excessively hot to touch. which of the following is the most likely
cause?
(A) High beams operated for too long
(B) Low current circuit breaker in circuit
(C) Relay coil partially shorted
(D) Corrosion causing high resistance at the connection - correct answer ✔✔(D) Corrosion
causing high resistance at the connection.
Exam)
Which of the following tests would be most efficient in identifying a high resistance in a starting
circuit?
(A) Disconnect battery, perform resistance test with an ohmmeter.
(B) Install ammeter, Perform a current draw test.
(C) Check the chassis data bus for fault codes
(D) Voltage drop test the circuit while cranking. - correct answer ✔✔(D) Voltage drop test the
circuit while cranking
When testing the specific gravity of the cells in a fully charged battery, one cell reads 1.220
while the others all read between 1.265 and 1.270. What should be done to the battery? -
correct answer ✔✔(B) Replace the battery
When testing alternator components, an ohmmeter reads 1 ohm between the rotor slip rings
and the rotor shaft. Which of the following is indicated?
(A) Reading is within specification
(B) Rotor windings are shortened to each other
(C) Rotor windings are shorted to ground
(D) Rotor windings are open - correct answer ✔✔(C) Rotor windings are shorted to ground
A heavy duty truck has no crank condition. Which of the following steps should be performed
first?
(A) Start grunt connection
(B) Start control circuit
(C) Starter solenoid
(D) Battery state of charge - correct answer ✔✔(D) Batter state of charge
,In order to test voltage drop through a starter circuit magnetic switch, which of the following
must be done?
(A) Remove the magnetic switch from the cranking circuit.
(B) Disconnect the starter solenoid to start strap
(C) Energize the control circuit
(D) Short through the magnetic switch load terminals - correct answer ✔✔(C) Energize the
control Circuit
If a truck alternator is full fielded in operation, which of the following will be the most likely
result?
(A) Maximum charging system current
(B) Batteries discharge rapidly
(C) Dim Lights
(D) Circuit breakers trip - correct answer ✔✔(A) Maximum charging system current
An alternator is carbon pile tested and has zero output. Which of the following is the most likely
cause?
(A) Battery is only 25% charged
(B) Truck and trailer electrical load exceeds alternator specifications
(C) Open alternator field circuit
(D) Loose drive belts - correct answer ✔✔(C) Open alternator field circuit
A fully charged batter is to be tested in a shop where the ambient temperature is above 21
degrees celsius. The state of charge test indicates 12.6 volts and when a carbon pile is used to
load the battery for the 15-second load test, the voltage bottoms at 9.3 volts. What should be
done? - correct answer ✔✔Replace the battery
, When branch testing a starter motor, the amperage draw exceeds the manufactures
specifications. Which of the following is the most likely cause?
(A) Shorted motor windings
(B) Burned solenoid contacts
(C) Open motor windings
(D) Insufficient brush spring tension - correct answer ✔✔(A) Shorted motor windings
The left turn lights on a tractor/trailer combination function on the tractor but not the trailer.
When checking the 7-pin trailer connector, which colour code assignment should be checked
first? - correct answer ✔✔(B) Yellow
A technician is measuring voltage drop across a triple cluster of three marker lights. Each is
tested by placing one voltmeter probe on the positive terminal and the other on the unit
ground terminal. Each of the three readings is almost identical. Which of the following readings
would suggest that the circuit is in good condition?
(A) 0.15 volts
(B) 0.80 volts
(C) 4 volts
(D) 12 volts - correct answer ✔✔((D) 12 volts
A headlight unit terminal feels excessively hot to touch. which of the following is the most likely
cause?
(A) High beams operated for too long
(B) Low current circuit breaker in circuit
(C) Relay coil partially shorted
(D) Corrosion causing high resistance at the connection - correct answer ✔✔(D) Corrosion
causing high resistance at the connection.
