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PMI ASE > Electrical/Electronics > Flashcards

Electrical/Electronics Flashcards

1
Q

Where should inspection of a battery begin?

A

An inspection of a battery should always begin with a thorough visual inspection of the case and the immediate surrounding area for any signs of leakage.
Check mounting bolts, hold-down clips, and cover clamps.
Ruber hold-downs and insulators should have no tears or cracks.

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2
Q

What are battery terminals?

A

Battery terminals are either two tapered posts or threaded studs on top of the case or two internally threaded connectors on the side. Some batteries have both types of terminals so that one battery fits either application.

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3
Q

What should be disconnected first when disconnecting a battery?

A

The ground cable should always be disconnected first, then the positive cable; therefore when reconnecting a battery, the positive cable should always be connected first and the ground cable last.

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4
Q

What kind of battery hook-ups do heavy-duty trucks us?

A

Heavy-duty trucks typically use three or four batteries connected in series or parallel to allow operation of a 123-volt or 24-volt electrical system, and/or to increase the cold cranking amperes (CCA) rating of the vehicle.

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5
Q

Which is the most common battery hookup?

A

The most common hookup is the parallel hookup, which can be further described as a single-path circuit or dual-path circuit.

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6
Q

How is the path determined?

A

The path is determined by the placement of batteries, such as two batteries per side or truck or all the batteries in one battery box on one side of the truck, or behind the cab.

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7
Q

How do you check the condition of the battery cables?

A

Check the condition of the battery cables by performing voltage drop tests.
Connect the voltmeter in parallel with the portion of the circuit being tested, being careful to observe polarity.

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8
Q

How do you test for resistance caused by battery terminal corrosion?

A

Place one voltmeter lead on the battery post, the other one on the cable, and then observe the meter while cranking the starter.
A good connection at the battery post will show that only about 0.1 volts are dropped.
When the voltage dropped across the entire positive battery cable measured there should be less than 0.5 volts dropped.
You can test the positive battery cable by placing one lead on the battery post and the other on the solenoid battery cable stud, testing voltage drop through the entire cable.

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9
Q

How do you test the ground circuit?

A

Place one lead on the negative battery post and the other on the starter frame and observe the voltage reading while cranking, There should be less than 0.3 volts dropped across the negative cable.

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10
Q

All wires somewhat resist current flow. What determines the value of resistance?

A

The value of resistance is relative to the size and type of wire used.
In relation to current flowing, the smaller the wire the greater the resistance value.
Resistance generates heat, which further increases resistance.

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11
Q

How do you clean a battery?

A

A battery can be cleaned with a baking soda and water solution.
Always wear hand and eye protection when servicing batteries and their components.

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12
Q

What is occurring when the built-in hydrometer indicates light yellow or clear?

A

The electrolyte level is low and the battery should be replaced.

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13
Q

How can a high voltage regulator setting result in low electrolyte levels?

A

By overcharging.

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14
Q

How can you prevent corrosion of the cable clamps?

A

By spraying the cable clamps with a protective coating.
Or a little grease or petroleum jelly will also prevent corrosion.
Also, protective pads that go under the clamp and around the terminal can prevent corrosion.

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15
Q

What should you do to the battery case, terminals and electrolyte level before testing?

A

Perform a visual inspection.

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16
Q

What should you do if you find any leakage from the case due to cracks or loose posts/terminals?

A

The battery is deemed unserviceable and must be replaced.

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17
Q

What comprises the level of electrolyte?

A

A combination of sulfuric acid and distilled water and it must be serviced if required.

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18
Q

What must be completely immersed in electrolyte?

A

The plate area must be completely immersed in electrolyte; if the level is low, indicated by the plate area being exposed then distilled water only can be added to return the electrolyte to proper balance.

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19
Q

Why can’t you use tap water to add to the electrolyte?

A

Tap water contains impurities and will lead to premature battery failure.

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20
Q

What are some things that usually indicate the overcharging of the battery?

A

A battery having moisture on the top surface
A strong odor of sulfur
Expanded case or
Excessively high temperatures

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21
Q

What does moisture on the surface of the battery cause?

A

A discharge condition and must be removed.

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22
Q

Cold weather starts are critical to the operation of a truck.
What can happen to a battery that is even partially discharged in cold weather?

A

It can e be exposed to a freeze-up in cold weather.

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23
Q

What happens to the specific gravity in a discharged battery?

A

It is decreased to a point where the electrolyte can freeze.

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24
Q

What can you use to determine the state of charge of a battery?

A

A battery open-circuit can be used to determine the sate of charge.

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25
Q

What state of a battery must have its surface charge removed before testing?

A

A battery that has recently been charged bu running the engine, or using a battery charger must ave its surface charge removed before testing.

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26
Q

How can you remove a surface charge?

A

Surface charge may be removed by applying a load of 300 amps for 15 seconds with a carbon pile load tester, or by cranking the engine fo 15 seconds.

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27
Q

What should you do after removing the surface charge?

A

After removing the surface charge, stabilize the voltage by allowing the battery to rest for 15 minutes.

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28
Q

If the State of Charge is fully charged, what is the stabilized open circuit voltage?

A

12.6 volts or more

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29
Q

If the State of Charge is 75% charged, what is the stabilized open circuit voltage?

A

12.4 volts

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30
Q

If the State of Charge is 50% charged, what is the stabilized open circuit voltage?

A

12.2 volts

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31
Q

If the State of Charge is 25% charged, what is the stabilized open circuit voltage?

A

12.0 volts

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32
Q

If the State of Charge is discharged, what is the stabilized open circuit voltage?

A

11.7 volts or less

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33
Q

If the battery passes the state of charge test, what test should you then perform and why?

A

Then, perform a load test to determine if the battery is capable of providing the proper discharge amperage and voltage under load conditions.

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34
Q

How long should you wait between load testing cycles?

A

A two minute waiting period should be maintained to avoid damage to the battery

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35
Q

If it is a multiple battery vehicle, what should your for recharging steps be?

A
  1. First, disconnect the batteries and perform individual testing of each battery.
  2. Determine the amperage rating of the vehicle (check Manufacturer’s specification), and confirm that the proper batteries are installed in the vehicle.
  3. If the voltage is below 12.4 volts DC at 70 degrees, the battery should be recharged to above 12.6 vols.
  4. Apply a load through the tester at one-half the CCA for 15 seconds.
    If the voltage drops below 9.6 volts at 70 degrees F, the battery is unserviceable.
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36
Q

Because charging to proper levels can take hours to properly complete, what would be good time management?

A

Install the battery charger, set it to a medium charge rate(voltage), amperage approximately 40 amps, and observe the voltage rate.
If the voltage exceeds 15 volts DC within 2 or 3 minutes, then the battery requires replacement.

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37
Q

What level of torque do starter motors produce and what should you do?

A

Check the clamping torque of the starter flange fasteners.

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38
Q

What are the components of the starting circuit?

A

The battery cables; magnetic switch or solenoid; and the starter motor.
Starter relays may be integral or non-integral with the starter.
External starter relays (“mag” switch) can attach either to the starter as a separate unit or to the firewall.

39
Q

What does the removal of integral or non-integral, or external starter relays entail?

A

Removal of these types of starter relays entails removing the two positive leads and the control wires.

40
Q

What kind of switch is the starter relay?

A

The starter relay is an electrical high-current switch and it does not have a ground lead.

41
Q

What should you do if the starter system has a magnetic switch?

A

Use a jumper wire around the heavy terminals.
If it cranks, the relay is defective assuming that control current from the starting switch is available at the small terminal of the relay.

42
Q

What should you do any time maintenance is to be performed on the starter?

A

Any time maintenance is performed on the starter, remove the ground (negative lead) from the battery to prevent accidental shorting of the wiring.

43
Q

Why is a voltmeter connected across a component in a circuit?

A

A voltmeter is connected across a component in a circuit to measure the voltage drop across the component.

44
Q

What must happen during a voltage drop test?

A

A current must be flowing through the circuit during the voltage drop test.
If a circuit has a normal resistance, the voltage drop is within specifications. For example with the engine cranking, the positive battery cable may have a 0.2-volt drop.

45
Q

What does excessive resistance in a cable o component cause?

A

It causes a higher than specified voltage drop and reduce current flow.

46
Q

What does the sum of the voltage drops in any series circuit equal?

A

It will equal the source voltage or applied voltage.

47
Q

While cranking the engine, if the starter is noisy while cranking the engine, what may be happening?

A

There may be loose or broken mounting bolts or the teeth on the flywheel or starter drive may be worn or damaged.

48
Q

What is the indication of a starter spinning without cranking the motor?

A

It is an indication of a worn starter drive or damage teeth.

49
Q

What is the result of an engine that cranks slowly or unevenly?

A

An engine that cranks slowly or unevenly can result in a no-start condition because a diesel engine has to reach a minimum cranking speed before it can start

50
Q

What could be the cause if the engine cranks over too slowly?

A

It could be caused by engine mechanical problems or it could be related to the starter. The starter may be receiving insufficient voltage or current from the battery.

51
Q

What are other noises to listen for when the engine cranks?

A

Other noises to listen for are a starter that chatters and disengages before the engine has started and a starter that engages but does not spin. Note these noises, so that more thorough testing can be performed.

52
Q

What do high starter current draw, low cranking speed, and low cranking voltage usually indicate?

A

A faulty motor.

53
Q

What do low starter current draw, low cranking speed, and high cranking voltage usually indicate?

A

Excessive resistance in the starting current/.

54
Q

What does the starting system carry?

A

The starting system carries the high current low within the system and supplies power for the actual engine cranking.

55
Q

What does the cranking current test or starter draw test measure?

A

The cranking current test or starter draw test measures the amount of current, in amperes, that the starter circuit draws to crank the engine.

56
Q

How is the amperage reading useful?

A

The amperage reading is useful in isolating the source of certain types of starter problems.

57
Q

What is an inoperative starter, along with a high current drawn indication of?

A

An inoperative starter, along with a high current drawn is an indication of a direct short to ground.

58
Q

What would cause an operative failure and a no-current condition?

A

Any opens, failed switches, spings, or relays.

59
Q

If the alternator mounting holes are distorted due to over-torquing and/or age what should you do?

A

Replace the alternator.

60
Q

What will severely out-of-round mounting holes on an alternator cause?

A

Will cause misalignment of the drive belt and may cause premature earing failure.

61
Q

When inspecting the alternator, what does a complaint of an unusual noise require and what will it determine?

A

A thorough visual inspection will usually determine whether a loose component is causing a vibration or any unusual sounds.

62
Q

Why is drive belt tension critical?

A

To prevent slippage.

63
Q

What must the minimum output requirement of the alternator (voltage and amperage) first e confirmed by?

A

The manufacturer’s specification.

64
Q

What makes the requirements exceed output?

A

Due to additional lighting, trailer, refrigeration unit, etc.

65
Q

At what speed is the output testing usually performed?

A

All testing is usually performed at 5,000 alternator rpm or 1500 to 2000 engine rpm for purposes of testing accuracy.

66
Q

If the vehicle is a late model and computer-controlled, why may the speed of 5,000 alternator rpm or 1500 to 2000 engine rpm not be possible?

A

Because the engine ECM will not permit anything above a preset limit when there is no load on the engine.

67
Q

How would you perform a battery testing, using a load tester unit?

A

Using a load tester unit, place the positive cable of the tester onto the positive battery cable and the negative cables onto the negative battery cable.
Then place the inductive pickup clamp of the tester around the output cable of the alternator.
The load tester should now indicate battery voltage
Start the engine, and raise the engine speed to the specified rpm.
Apply a load using the carbon pile until the specified maximum amperage is read without dropping system voltage below 13 volts.
Alternator output should be within 10% of the specified rating.
As ambient temperature increases, alternator output may decrease.

68
Q

What other tests can you perform along with an alternator voltage output test?

A

The voltage test can be used in conjunction with performing alternator current output test, as the amperage out of the alternator will have an effect upon the voltage being produced.

69
Q

How is the voltage output of the alternator to be measured?

A

It is to be measured with the engine running, at the alternator output terminal, using a voltmeter.
Output will depend on the load.

70
Q

Where is the in-dash type voltmeter usually connected?

A

At or near the battery.

71
Q

How do you verify the voltage accuracy of the dash voltmeter?

A

Connect the test meter on the battery terminals in proper polarity; the meter reading of the test and dash unit should be within a 1/2 volt DC of the test unit.

72
Q

Are inoperative interior lighting considered as a basis for placing a vehicle out of service?

A

No, but it is still important for the safe operation of the truck.

73
Q

What operates the dome lights and luggage compartment lights?

A

A door jamb switch that completes the ground circuit When the door is open, the light should come on.
Some interior compartment lights use a mercury switch that closes when the door is opened.

74
Q

When does dash lighting operate?

A

When the lights are on and the dimmer should adjust them to the desired level

75
Q

What are the common lighting problems?

A

Power supply, ground, and bulbs.

76
Q

What could be the cause if all of the interior lights are dim?

A

The cab may not be adequately grounded. This is especially true when lights are attached to plastic panels, and the ground must be completed elsewhere.

77
Q

With what and how would you test continuity in an electric circuit?

A

Continuity in an electric circuit may be tested with a high-impedance digital voltmeter.
1. Connect the meter ground lead to a satisfactory ground connection and connect the positive meter lead to various locations in the circuit staring at the voltage source.
When the meter reads a very low voltage, the open circuit is between the meter positive lead and the previous location where a normal voltage reading was obrained.

78
Q

What would you use a 12-volt test light and a high-impedance test light to test?

A

a 12-volt test light may be used to test continuity in a circuit but a high-impedance test light must be used when testing continuity in computer-controlled circuits

79
Q

How should you use an ohmmeter to test continuity?

A

If an ohmmeter is used to test continuity, the meter leads must be connected across the terminals on the component fo be tested with the component disconnected from the circuit.

80
Q

How may an ohmmeter be damaged?

A 
An ohmmeter may be damaged it it is connected to a circuit with voltage supplied to the circuit.  Always disconnect the truck's battery before using a self-powered test lamp to test continuity.
Never use a self-powered test lamp on an electronic module circuit, because damage of the module may result.
81
Q

What exterior lights are generally mounted on the sides?

A

Depending on cab design, are turn signal lights, side-marker indicators, and sometimes an intermedia turn signal.

82
Q

What exterior lights are generally mounted on the roof?

A

Clearance lights (usually on either end), identification lights (usually in the middle), and sometimes additional utility lights.

83
Q

What exterior lights are generally mounted on the front?

A

Single or dual headlights, fog lights turn-signal lights, and sometimes additional utility lights.

84
Q

What must be checked first in order to adjust the headlights?

A

Headlight aim must be checked first

85
Q

If headlight aiming equipment is not available, how can you check headlight aiming?

A

Headlight aiming can be checked by projecting the upper beam of each light upon a screen or hart at a distance of 25 feet ahead of the headlights. The vehicle should be exactly perpendicular to the chart.

86
Q

When should an operational check of the brake light switch be performed?

A

An operational check of the brake light switch should be performed during a check of the electrical system since the brake light or stoplight switch is part of the vehicle’s electrical system.

87
Q

What are the most common sources of dim lights?

A

Defective and/or improper ground connections.

88
Q

Besides replacing defective lamps and bulbs, what else should you check?

A

Periodically check to see that all wiring connections are clean and tight; that lamp units are tightly mounted o provide a good ground and headlights are properly adjusted.

89
Q

Where is the junction block for the trailer lights located?

A

Inside the cab, often directly behind the driver seat.

90
Q

How do you gain access to the junction block?

A

By removing a plastic cover held in place by four screws.

91
Q

In sleeper models, where is the junction block located?

A

In the luggage compartment.

92
Q

Why does the inspector usually start at the front and work back when performing a lighting inspection?

A

Because the source of power is usually upfront

93
Q

Do modern box trailers have a junction box? Why or why not?

A

There are no splices for corrosion to attack and the trailer junction box has been eliminated.

94
Q

What kind of trailer plug and connector do most current vehicles use?

A

A seven-wire trailer plug and connector.

PMI ASE (5 decks)

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