2. OBJECTIVES
After studying Chapter 10, the reader should be able to:
Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A” (General Electrical/Electronic Systems Diagnosis).
Explain the wire gauge number system.
Describe how fusible links and fuses protect circuits and wiring.
List the steps for performing a proper wire repair.

3. AUTOMOTIVE WIRING
Most automotive wire is made from strands of copper covered by insulating plastic.

4. AUTOMOTIVE WIRING American Wire Gauge
Wiring is sized and purchased according to gauge size as assigned by the American wire gauge (AWG) system.
AWG numbers can be confusing because as the gauge number increases, the size of the conductor wire decreases.
Therefore, a 14 gauge wire is smaller than a 10 gauge wire.

5. AUTOMOTIVE WIRING American Wire Gauge

6. AUTOMOTIVE WIRING Metric Wire Gauge
Most manufacturers indicate on the wiring diagrams the metric wire gauge sizes measured in square millimeters (mm2) of cross-sectional area.

7. AUTOMOTIVE WIRING Metric Wire Gauge

8. BRAIDED GROUND STRAPS
All vehicles use ground straps between the engine and body and/or between the body and the negative terminal of the battery.
Many of the engine-to-body straps are braided ground straps and are uninsulated.
FIGURE 10-1 All lights and accessories ground to the body of the vehicle. Body ground wires such as this one are needed to conduct all of the current from these components back to the negative terminal of the battery. The body ground wire connects the body to the engine. Most battery negative cables attach to the engine.

9. BATTERY CABLES
Battery cables are the largest wires used in the automotive electrical system.
The cables are usually 4 gauge, 2 gauge, or 1 gauge wires (19 mm2 or larger).
FIGURE 10-2 Battery cables are designed to carry the heavy starter current and are therefore usually 4 gauge or larger wire. Auxiliary wiring for accessories and other electrical components is also connected to the positive battery cable on this vehicle. The plastic conduit (also called split-loom tubing) reduces the risk of damage.

10. JUMPER CABLES
Jumper cables are 4 to 2/0 gauge electrical cables with large clamps attached and are used to connect a vehicle that has a discharged battery to a vehicle that has a good battery.

11. FUSES AND CIRCUIT PROTECTION DEVICES
Fuses should be used in every circuit to protect the wiring from overheating and damage caused by excessive current flow as a result of a short circuit or other malfunction.
Many fuses are used to protect more than one circuit of the automobile.

12. FUSES AND CIRCUIT PROTECTION DEVICES
FIGURE 10-3 A typical automotive fuse panel.

13. FUSES AND CIRCUIT PROTECTION DEVICES Blade Fuses
The color of the plastic of blade fuses indicates the maximum current flow, measured in amperes.

14. FUSES AND CIRCUIT PROTECTION DEVICES Blade Fuses
FIGURE 10-4 Blade-type fuses can be tested through openings in the plastic at the top of the fuse.

15. FUSES AND CIRCUIT PROTECTION DEVICES Mini Fuses
To save space, many vehicles use mini (small) blade fuses.
FIGURE 10-5 Three sizes of blade-type fuses: mini on the left, standard
or ATO type in the center, and maxi on the right.

16. FUSES AND CIRCUIT PROTECTION DEVICES Maxi Fuses
Maxi fuses are a large version of blade fuses and are used to replace fusible links in many vehicles.

17. FUSES AND CIRCUIT PROTECTION DEVICES Pacific Fuse Element
First used in the late 1980s, Pacific fuse elements (also called a fuse link or auto link) are used to protect wiring from a direct short-to-ground.
FIGURE 10-6 A comparison of the various
types of protective devices used in most vehicles.

18. FUSES AND CIRCUIT PROTECTION DEVICES Testing Fuses
It is important to test the condition of a fuse if the circuit being protected by the fuse does not operate.
Most blown fuses can be detected quickly because the center conductor is melted.
FIGURE 10-7 To test a fuse, use a test light to check for power at the power side of the fuse. The ignition switch and lights may have to be on before some fuses receive power. If the fuse is good, the test light should light on both sides (power side and load side) of the fuse.

19. FUSES AND CIRCUIT PROTECTION DEVICES Circuit Breakers
Circuit breakers are used to prevent harmful overload (excessive current flow) in a circuit by opening the circuit and stopping the current flow to prevent overheating and possible fire caused by hot wires or electrical components.

20. FUSES AND CIRCUIT PROTECTION DEVICES Circuit Breakers
FIGURE 10-8 Typical blade circuit breaker fits into the same space as a blade fuse.
If excessive current flows through the bimetallic strip, the strip bends and opens the
contacts and stops current flow. When the circuit breaker cools, the contacts close again,
completing the electrical circuit.

21. FUSES AND CIRCUIT PROTECTION DEVICES Circuit Breakers
Examples are the circuits for the following accessories.
Power seats
Power door locks
Power windows
FIGURE 10-9 These electrical symbols are used to represent circuit
breakers.

22. FUSES AND CIRCUIT PROTECTION DEVICES PTC Circuit Protectors
Positive temperature coefficient (PTC) circuit protectors are solid state (without moving parts).
Unlike circuit breakers or fuses, PTC circuit protection devices do not open the circuit, but provide a very high resistance between the protector and the component.
FIGURE (a) Normal operation of a PTC circuit protector in a power window motor circuit. Note the many conducting paths. With normal current flow, the temperature of the PTC circuit protector remains normal. (b) When current exceeds the amperage rating of the PTC circuit protector, the polymer material that makes up the electronic circuit protector increases in resistance. As shown here, a high-resistance electrical path still exists even though the motor will stop operating as a result of the very low current flow through the very high resistance. The circuit protector will not reset or cool down until voltage is removed from the circuit.

23. FUSES AND CIRCUIT PROTECTION DEVICES PTC Circuit Protectors
The electronic control unit (computer) used in most vehicles today incorporates thermal overload protection devices.
FIGURE PTC circuit protectors are used extensively in the power distribution center of this Chrysler vehicle.

24. FUSES AND CIRCUIT PROTECTION DEVICES Fusible Links
A fusible link is a type of fuse that consists of a short length of standard copper-strand wire covered with a special nonflammable insulation.

25. FUSES AND CIRCUIT PROTECTION DEVICES Fusible Links
FIGURE Fusible links are usually located close to the battery and are usually attached to a junction block. Notice that they are only 6 to 9 in. long and feed more than one fuse from each fusible link.

26. FUSES AND CIRCUIT PROTECTION DEVICES Fusible Links
Fusible links are installed as close to the battery as possible so that they can protect the wiring and circuits coming directly from the battery.

27. FUSES AND CIRCUIT PROTECTION DEVICES Fusible Links
FIGURE (a) Demonstration showing the function of a fusible link by connecting a battery to each end with jumper cables. (b) After about 1 to 2 seconds, smoke starts to roll out from around the insulation. (c) After about 5 seconds, smoke fills the area as the wire inside finally melts and breaks (opens) the circuit. (d) The fusible link afterward .Notice that the special high-temperature insulation is unharmed even though the copper conductor has melted in half.

28. FUSES AND CIRCUIT PROTECTION DEVICES Checking Fusible Links
Fusible links can melt and not show any external evidence of damage.
To check a fusible link, gently pull on each end to see if it stretches.
If the insulation stretches, then the wire inside has melted and the fusible link must be replaced after determining what caused the link to fail.

29. TERMINALS AND CONNECTORS
A terminal is a metal fastener attached to the end of a wire, which makes the electrical connection.
The term connector usually refers to the plastic portion that snaps or connects together, thereby making the mechanical connection.

30. TERMINALS AND CONNECTORS
FIGURE Some terminals have seals attached to help seal the electrical connections.

31. TERMINALS AND CONNECTORS
FIGURE Separate a connector by opening the lock and pulling the two apart.
FIGURE The secondary locks help retain the terminals in the connector.

32. TERMINALS AND CONNECTORS
FIGURE Use a small removal tool, sometimes called a pick, to release terminals from the connector.

33. WIRE REPAIR Solder
Solder is an alloy of tin and lead used to make a good electrical contact between two wires or connections in an electrical circuit.
FIGURE Always use rosin-core solder for electrical or electronic soldering. Also, use small-diameter solder for small soldering irons. Use large-diameter solder only for large-diameter (large-gauge) wire and higher wattage soldering irons (guns).

34. WIRE REPAIR Solder
Soldering a wiring splice includes the following steps.
While touching the soldering gun to the splice, apply solder to the junction of the gun and the wire.
The solder will start to flow. Do not move the soldering gun.
Just keep feeding more solder into the splice as it flows into and around the strands of the wire.
After the solder has flowed throughout the splice, remove the soldering gun from the splice and allow the solder to cool slowly.

35. WIRE REPAIR Crimping Terminals
Terminals can be crimped to create a good electrical connection if the proper type of crimping tool is used.

36. WIRE REPAIR Crimping Terminals
FIGURE Notice that to create a good crimp the open part of the terminal is placed in the jaws of the crimping tool toward the anvil or the W-shape part.
FIGURE All hand-crimped slices or terminals should be soldered to be assured of a good electrical connection. Good fillets means that the solder should flow slightly from the clip and be smooth and shiny in appearance.

37. WIRE REPAIR Heat Shrink Tubing
Heat shrink tubing is usually made from polyvinyl chloride (PVC) or polyolefin and shrinks to about half of its original diameter when heated; this is usually called a 2:1 shrink ratio.
FIGURE A butane torch especially designed for use on heat shrink applies heat without an open flame, which could cause damage.

38. WIRE REPAIR Crimp-and-Seal Connectors
Crimp-and-seal connectors contain a sealant and shrink tubing in one piece and are not simply butt connectors.
FIGURE A typical crimp-and-seal connector. This type of connector is first lightly crimped to retain the ends of the wires and then it is heated. The tubing shrinks around the wire splice and a thermoplastic glue melts on the inside to provide an effective weather-resistant seal.

39. WIRE REPAIR Crimp-and-Seal Connectors
The usual procedure specified for making a wire repair using a crimp-and-seal connector is as follows:
Strip the insulation from the ends of the wire (about 5/16 in. or 8 mm).
Select the proper size of crimp-and-seal connector for the gauge of wire being repaired. Insert the wires into the splice sleeve and crimp.
Apply heat to the connector until the sleeve shrinks down around the wire and a small amount of sealant is observed around the ends of the sleeve.

40. WIRE REPAIR Crimp-and-Seal Connectors
FIGURE The left side of this crimp-and-seal connector has been gently crimped and heated. Note how the connector has shrunk down
around the wire. The heat has also released a thermal sealant that forms an effective environmental seal around the wire.

41. WIRE REPAIR Aluminum Wire Repair
Many automobile manufacturers use plastic-coated solid aluminum wire for some body wiring.
Because aluminum wire is brittle and can break as a result of vibration, it is only used where there is no possible movement of the wire, such as along the floor or sill area.

42. WIRE REPAIR Aluminum Wire Repair
Step 1 Carefully strip only about 1/4 in. (6 mm) of insulation from the aluminum wire, being careful not to nick or damage the aluminum wire case.
Step 2 Use a crimp connector to join two wires together. Do not solder an aluminum wire repair. Solder will not readily adhere to aluminum because the heat causes an oxide coating on the surface of the aluminum.
Step 3 The spliced, crimped connection must be coated with petroleum jelly to prevent corrosion.
Step 4 The coated connection should be covered with shrinkable plastic tubing or wrapped with electrical tape to seal out moisture.

43. SUMMARY The higher the AWG size number, the smaller the wire.
Metric wire is sized in square millimeters (mm2) and the higher the number, the larger the wire.
All circuits should be protected by a fuse. The current in the circuit should be about 80% of the fuse rating.
Circuit breakers and fusible links are other circuit protection devices.
A terminal is the metal end of a wire, whereas a connector is the plastic housing for the terminal.
All wire repair should use either soldering or a crimp-and-seal connector

44. REVIEW QUESTIONS
Describe the American wire gauge (AWG) system and compare it with the metric system.
Explain the difference between a wire and a cable.
Explain the difference between a terminal and a connector.
Discuss how fuses, PTC circuit protectors, circuit breakers, and fusible links protect a circuit.
Describe how to perform a wire repair.

45. The higher the AWG number, _____.
CHAPTER QUIZ
The higher the AWG number, _____.
The smaller the wire
The larger the wire
The thicker the insulation
The more strands in the conductor core

46. The higher the AWG number, _____.
CHAPTER QUIZ
The higher the AWG number, _____.
The smaller the wire
The larger the wire
The thicker the insulation
The more strands in the conductor core

47. CHAPTER QUIZ 2. Metric wire size is measured in units of _____. Meters
Cubic centimeters
Square millimeters
Cubic millimeters

48. CHAPTER QUIZ 2. Metric wire size is measured in units of _____. Meters
Cubic centimeters
Square millimeters
Cubic millimeters

49. 3. Which statement is true about fuse ratings?
CHAPTER QUIZ
3. Which statement is true about fuse ratings?
The fuse rating is measured in volts.
The fuse rating should be higher than the normal current for the circuit.
A replacement fuse rating should be the same as the original fuse.
Both b and c are correct.

50. 3. Which statement is true about fuse ratings?
CHAPTER QUIZ
3. Which statement is true about fuse ratings?
The fuse rating is measured in volts.
The fuse rating should be higher than the normal current for the circuit.
A replacement fuse rating should be the same as the original fuse.
Both b and c are correct.

51. CHAPTER QUIZ
4. Which statements are true about wire, terminals, and connectors?
Wire is called a lead, and the metal end is a connector.
A connector is usually a plastic piece where terminals lock in.
A lead and a terminal are the same thing.
Both a and c are correct.

52. CHAPTER QUIZ
4. Which statements are true about wire, terminals, and connectors?
Wire is called a lead, and the metal end is a connector.
A connector is usually a plastic piece where terminals lock in.
A lead and a terminal are the same thing.
Both a and c are correct.

53. CHAPTER QUIZ
5. The type of solder that should be used for electrical work is _____.
Rosin core
Acid core
60/40 with no flux
50/50 with acid paste flux

54. CHAPTER QUIZ
5. The type of solder that should be used for electrical work is _____.
Rosin core
Acid core
60/40 with no flux
50/50 with acid paste flux

55. CHAPTER QUIZ
6. A technician is performing a wire repair on a circuit that uses 18 gauge wire. The parts department does not have 18 gauge wire but it does have 16 gauge wire and 20 gauge wire. Technician A says to use the 16 gauge wire. Technician B says to use the 20 gauge wire. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

56. CHAPTER QUIZ
6. A technician is performing a wire repair on a circuit that uses 18 gauge wire. The parts department does not have 18 gauge wire but it does have 16 gauge wire and 20 gauge wire. Technician A says to use the 16 gauge wire. Technician B says to use the 20 gauge wire. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

57. CHAPTER QUIZ
7. Two technicians are discussing fuse testing. Technician A says that a test light should light on both test points of the fuse if it is okay. Technician B says the fuse is defective if a test light only lights on one side of the fuse. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

58. CHAPTER QUIZ
7. Two technicians are discussing fuse testing. Technician A says that a test light should light on both test points of the fuse if it is okay. Technician B says the fuse is defective if a test light only lights on one side of the fuse. Which technician is correct?
Technician A only
Technician B only
Both Technicians A and B
Neither Technician A nor B

59. CHAPTER QUIZ
8. If a wire repair, such as that made under the hood or under the vehicle, is exposed to the elements, which type of repair should be used?
Wire nuts and electrical tape
Solder and adhesive-lined heat shrink or crimp-and-seal connectors
Butt connectors
Rosin-core solder and electrical tape

60. CHAPTER QUIZ
8. If a wire repair, such as that made under the hood or under the vehicle, is exposed to the elements, which type of repair should be used?
Wire nuts and electrical tape
Solder and adhesive-lined heat shrink or crimp-and-seal connectors
Butt connectors
Rosin-core solder and electrical tape

61. CHAPTER QUIZ
9. Many ground straps are uninsulated and braided because _____.
They are more flexible to allow movement of the engine without breaking the wire
They are less expensive than conventional wire
They help dampen radio-frequency interference (RFI)
Both a and c are correct

62. CHAPTER QUIZ
9. Many ground straps are uninsulated and braided because _____.
They are more flexible to allow movement of the engine without breaking the wire
They are less expensive than conventional wire
They help dampen radio-frequency interference (RFI)
Both a and c are correct

63. CHAPTER QUIZ 10. What causes a fuse to blow?
A decrease in circuit resistance
An increase in the current flow through the circuit
A sudden decrease in current flow through the circuit
Both a and b

64. CHAPTER QUIZ 10. What causes a fuse to blow?
A decrease in circuit resistance
An increase in the current flow through the circuit
A sudden decrease in current flow through the circuit
Both a and b

65. END