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het2 > 205B - Charging System Testing And Service > Flashcards

205B - Charging System Testing And Service Flashcards

1
Q

What would result from an alternator drive belt that is in poor condition and not tensioned properly?

A
  • An undercharged battery
  • Glazing

205B pg. 2

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2
Q

What does glazing refer to regarding alternator belts?

A

A shiny sidewall caused by heat friction when a loose belt slips in the pulley. Also caused by oil or grease on the pulleys.

205B pg. 2

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3
Q

What can cause alternator belts to separate?

A

Oil, grease, belt dressing.

205B pg. 3

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4
Q

What causes jagged or streaked sidewalls on alternator belts?

A

Foreign objects such as sand or small gravel embedded in the pulley drive surface.

205B pg. 3

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5
Q

What could cause tensile breaks in alternator belts?

A

Breaks in the belt’s cord body.

  • Large foreign objects embedded in the pulley
  • Chips in pulley wear surface
  • Prying on the belt to force it onto pulleys during installation.

205B pg. 4

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6
Q

Multi-ribbed belts must be checked for ______.

A

Uneven ribs

205B pg. 4

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7
Q

What damage to a belt could an undersized backside idler pulley result in?

A

Evenly spaced deep bottom cracks from the belt being over-flexed.

205B pg. 5

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8
Q

What could result from an over-tensioned alternator belt?

A

-Premature belt wear
- Alternator & pulley bearing damage

205B pg. 6

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9
Q

Multi-ribbed belts are tensioned with the use of a ____________.

A

Spring-operated belt tensioner

205B pg. 7

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10
Q

How are multi-ribbed belts checked for the proper tension?

A

Confirm that the tensioner arm is operating in the proper zone.

205B pg. 7

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11
Q

What is the maximum allowed offset of alternator pulleys?

A

1mm over a 20cm distance

205B pg. 8

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12
Q

How are high resistances checked for in a charging circuit?

A
  • With a carbon pile, draw the rated amperage of the alternator from the battery
  • Test from alternator positive to battery positive for voltage drop
  • Test from alternator negative to battery negative for voltage drop

Max 0.5V total voltage drop for 12V system
Max 1V total voltage drop for 24V system

205B pg. 10

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13
Q

What could be indications of a charging system that is not completely charging the batteries? (4)

A
  • Slow or no engine cranking
  • Low voltmeter reading
  • Dim work lights
  • Slow cycling of equipment warning lights

205B pg. 12

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14
Q

What could be indications of a charging system that is overcharging the batteries? (4)

A
  • High voltmeter readings
  • Lights burn out rapidly or run bright
  • Battery emitting fumes
  • Battery spilling acid or swelling

205B pg. 13

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15
Q

Why do equipment battery groups need to have batteries with balanced internal resistances?

A
  • To satisfactorily crank the engine for startup
  • To equally charge all batteries

205B pg. 14

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16
Q

What is the OCV of a 12V & 24V system?

A

12.6V
25.2V

205B pg. 16

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17
Q

When multiple batteries are used in a system, why is it good practice to test each battery individually?

A

Testing across all batteries may not reveal a low battery or one in poor condition.

205B pg. 16

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18
Q

How is regulated voltage output of an alternator tested?

A
  • Turn off all electrical loads
  • Set the engine speed to provide maximum alternator output (approx 5000 alternator rpm)
  • After 2 minutes measure the voltage across the alternator output and ground.

Must be within 13.8V-14.8V (27.6V-29.6V for 24V)

The alternator output must not be more than 30% of the rated output when testing the voltage regulator.

205B pg. 17

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19
Q

How is alternator output amperage tested?

A
  • Set the engine to fast idle
  • Adjust carbon pile until the ammeter reads its highest value
  • Record highest amperage value and note voltage reading (must not drop below 12.6V on a 12V system, 25.2V on 24V system)

Measured current output must be within 10% of rated current output. If not, allow carbon pile to cool, repeat test.

205B pg. 18

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20
Q

What are some of the most common internal alternator faults?

A
  • Open field winding
  • Shorted stator
  • Open stator
  • Shorted diode
  • Open diode

205B pg. 19

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21
Q

What would result from a shorted stator winding?

A
  • Decreased current output due to the reduction in coil windings being cut by the rotor’s magnetic field.
  • Whining sounds

205B pg. 19

22
Q

What would result from an open in a stator winding?

A

Greatly reduced current output. (Greater reduction in output than a stator winding short)

205B pg. 20

23
Q

What would result from a shorted diode in an alternator’s rectifier bridge?

A
  • Reduction of 60% - 70% incurred output
  • Whining sound
  • Overheating

205B pg. 20

24
Q

What would result from an open diode in an alternator rectifier bridge?

A
  • Reduction of 33% in current output
  • Whining sound

205B pg. 21

25
Q

What is being tested in the pictures?
Is it in good condition?

A

Diode trio check.
In good condition.

205B pg. 25

26
Q

What is a visible sign of an overheated stator?

A

Blackened varnish insulation that becomes brittle and flakes off.

205B pg. 26

27
Q

What is being tested in the pictures? Is it in good or poor condition?

A

Stator ground test.
In good condition.

205B pg. 27

28
Q

What is being tested in the pictures? Is it in good or poor condition?

A

Rotor ground fault test.
In good condition.

205B pg. 28

29
Q

What is being tested in the pictures? Is it in good or poor condition?

A

Rotor winding resistance.
In good condition.

205B pg. 29

30
Q

How should alternator rotor slip rings be cleaned or refinished?

A

With 400 grit or finer sandpaper.

205B pg. 30

31
Q

How much wear is acceptable for alternator brushes?

A
  • Worn no more than 1/2 of new length
  • No burns, cracks, or broken

205B pg. 31

32
Q

Can rotor brush springs be stretched back to original length if their tension has been lost?

A

No

205B pg. 31

33
Q

Capacitors are tested for what three things?

A
  • Capacity
  • Leakage
  • Series resistance

205B pg. 32

34
Q

How is an alternator regulator tested?

A
  • Connect a test light to the brush output of the regulator
  • Connect the regulator to a power supply and gradually increase the voltage
  • Test light should turn on and remain on until voltage level reaches range of 13.8V-14.8V (27.6V-29.6V for 24V)

205B pg. 33

35
Q

Can petroleum-based solvents be used to clean stator and rotor windings?

A

No. Will dissolve the insulation layer causing shorts and ground faults.

Electrical parts cleaner such as CRC Lectra-Motive or GE Electrosol should be used.

205B pg. 33

36
Q

Should rosin-based or acid-based solder flux be used on electrical terminals?

A

Rosin-based flux. Acid-based flux will cause corrosion.

205B pg. 35

37
Q

If original alternator brushes are to be reused, how should they be cleaned?

A
  • 400 grit or finer sandpaper
  • Electrical contact cleaner
  • Make sure wear pattern matches the slip ring radius

205B pg. 37

38
Q

What two types of sounds can alternators emit which can help with troubleshooting?

A
  • Electrically generated
  • Mechanically generated

205B pg. 40

39
Q

What could be attached to an alternator to reduce radio frequency interference?

A

Capacitor.
Also protects alternator internal components from voltage spikes.

205B pg. 40

40
Q

What failed components could lead to electrically generated alternator sounds?

A
  • Shorted or open stator
  • Shorted or open rectifier diodes

205B pg. 40

41
Q

What could cause mechanically produced sounds on an alternator?

A
  • Loose alternator mounting bolts/bracket
  • Loose drive belt
  • Worn drive pulley
  • Rough or dry alternator bearings

205B pg. 40

42
Q

When boosting or fast charging a battery, what is the maximum voltage that should be applied?

A

Max 15.5V on 12V system
Max 31V on 24V system

205B pg. 43

43
Q

Unwanted high resistances in the electrical insulated and ground connections between the equipment’s batteries, starter, and alternator can be eliminated by: (2)

A
  • Tightening all connections
  • Cleaning off corrosion
44
Q

True or False
The voltage regulator senses the electrical load placed on the alternator by the vehicle’s battery and accessories.

A

False.
Regulator senses the battery voltage.

45
Q

True or False
Alternators create electrical energy by moving the electrical conductor through a magnetic field.

A

False.
Magnetic field (rotor) is moved across the conductor (stator)

46
Q

True or false
There are the same number of loops in each stator winding as there are north and south poles on the rotor.

A

True

47
Q

What is the typical current flow through alternator rotor windings?

A

2-10 amps

48
Q

What should an ohmmeter read across the rotor slip rings?

A

Approximately 1-7 ohms

49
Q

How would an A type alternator be manually full-fielded?

A

Ground the field terminal

50
Q

How would a B type alternator be manually full-fielded?

A

Jump power to the field terminal.

51
Q

If a non-working alternator was full-fielded and then started to work, what component in the alternator is defective?

A

Regulator

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