Electrical Service & Diagnosis. ATASA 5 th. ATASA 5 TH Study Guide Chapter 16 Pages Electrical Service & Diagnosis 70 Points

Transcription

1 ATASA 5 TH Study Guide Chapter 16 Pages Points Please Read the Summary

2 1. All Electrical problems can be categorized into one of three categories: Open Consumer Opens Shorts Open Conductive Path High Resistances

3 OPENS occur when a circuit is incomplete. Open Consumer Open Conductive Path

4 2. An problem prevents a circuit from operating. Open Short High Resistance

5 2. A to ground reduces resistance and increases current flow to blow the fuse. Open Short High Resistance

6 2. A to power or short to hot energizes an unwanted circuit. Open Short High Resistance

7 SHORTS occur when a circuit has an unwanted path for current. 12 v. source 2 amp normal current flow _ + 6 Ω resistor 1 Ω in shorting wire causes 12 amps of flow & blows the fuse when the switch is turned on

8 SHORTS occur when a circuit has an unwanted path for current. + _ 1 Ω in shorting wire causes 12 amps of flow & blows the fuse as soon as the fuse is replaced

9 SHORTS occur when a circuit has an unwanted path for current. + _ Short to hot energizes the circuit at all times

10 + H _ H + _ Horn circuit uses ground side switching. Short to ground energizes this circuit at all times.

11 2. High resistance in a path reduces flow. (less intensity in bulbs, less speed in motors) Voltage Current (amperage) Resistance

12 Parallel Lighting Circuit that is ground side switched + _

13 HIGH RESISTANCE occurs when there is unwanted resistance (corrosion). + _ High Resistance in common Ground Path decreases intensity (amps) in both bulbs

14 HIGH RESISTANCE occurs when there is unwanted resistance (corrosion). + _ High Resistance in one Ground Path decreases intensity (amps) in only one bulb

15 3. Many sensors are fed a volt reference signal. Bad grounds (those with excess resistance) can result in higher than normal readings back to the PCM. 5 volt 12 volt 42 volt

16 4. Wiring diagrams called show how a circuit is constructed or arranged. Pneumatics Schematics Fanatics

17 5. Common electric are used in schematic drawings. Some feature color coded wiring that indicates the color of the wire insulation, but no length or location is depicted. Cymbals Symbols Shapes

18 Ground Battery Resistor Variable Resistor Capacitor Fuse Circuit Breaker Thermistor Motor Momentary Switch Switch SPST Connector Lamp or Bulb Coil of Wire NPN Transistor PNP Transistor Diode LED Transformer DMM Relay Wye wound Coil Delta wound Coil Contacts

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20 6. Besides multi meters, wires, test lights and logic probes are used for diagnosis. Jumper Bumper Thumper

21 7. Non powered 12 volt test lights are used to check for voltage. Drops Available Consumption

22 8. A test light is used to check for continuity. 12 Volt Self Powered 1.5 Volt

23 Logic Probe

24 9. are fast reacting meters that measure & display voltage over time. Lab Rats Lab Tasks Lab Scopes

25 10. A good can do so much more than just read DTC s! Be sure to use the serial data stream, check TSB s, use the pattern failure troubleshooter, and all of the modes. Lead Tech Scan Tool Auto Teacher

26 11. Jumper wires with a or a circuit breaker can be used to by pass wires or switches. Do not use a jumper wire to by pass a consumer or a load. The circuit amps will skyrocket. Fuse Splice Ground

27 12. A computer will preserve power to volatile RAMs when the battery is disconnected for service. Note: The SIR system retains its back up power with a memory saver! Battery Saver Memory Saver RAM/ROM

28 13. A DMM used on computer circuits should have an input of 1 MΩ to 10 MΩ. Resistance Impedance Capacitance

29 14. A DMM used on high voltage hybrid vehicles should be ANSI & SCA 1000 V rated. CAT I CAT II CAT III

30 15. The auto feature on meters detects the proper range & sets the meter to read it. Ranging MN/MAX Averaging

31 16. A DMM set to measure volts is connected in to a circuit. Series Parallel Inductively

32 12.6 V Source Voltage V Ω A V A OFF V Ω C OM A Current Clamp Carbon Pile

33 17. Voltage tests will find excessive resistance that may not be detected with an ohmmeter. Think of Voltage Drop as Voltage Use by a consumer Drop Available Capacitance

34 0.2 V Voltage Drop V Ω A V OFF A Carbon Pile A V Ω COM Current Clamp

35 18. Ammeters are connected either in series or using pickups to measure current. Inductive Deductive Conductive

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37 19. Ohmmeters are always used on components disconnected from their source. (open = OL) Voltage Amperage Resistance

38 Remember to Zero your meter before you start measuring!

39 20. The DMM test mode (alert) sounds an audible beep when continuity exists. Continuity Hertz Smooth

40 21. The DMM / is a record function that is useful in capturing intermittent problems. MIN/MAX Pulse Width Smooth

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44 22. A DMM may also measure which is a percentage of circuit on time. normally measured in milliseconds, and in hertz. Duty Cycle, Pulse Width, Frequency

45 23. On a lab scope, voltage is shown on the axis. Vertical Horizontal Z

46 24. On a lab scope, time is shown on the axis. Vertical Horizontal Z

47 25. Lab scopes can display momentary electrical noise, disturbances, and signal. Glitches Snitches Sandwiches

48 Note: The sweep of a scope pattern is another name for the time axis.

49 Frequency is a term that describes how often a signal performs a complete cycle.

50 A cycle is a description of the changes that a signal goes through without repeating itself.

51 Frequency is measured in Hertz. Hertz is a measurement of Cycles per Second.

52 26. An scope is a real time scope. A is a Digital Storage Oscilloscope. Analog, Digital

53 27. Using a DSO, a technician can or capture a signal for closer analysis. Freeze Pinpoint Movie

54 Cursors can be used to measure time between 2 points horizontally. Cursors can be used to measure voltage between 2 points vertically.

55 28. A multiple DSO can display more than one waveform at a time for comparison. Base Face Trace

56 B 1, S 1 HO2S B 1, S 2 HO2S

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59 29. Waveform amplitude is shown as & waveform frequency is shown as. Voltage, Frequency

60 30. One complete sine wave is a. One cycle per second is 1 hertz. V O L T A G E TIME Cycle Frequent Repeat

61 31. A is a DMM that displays voltage, resistance, current & frequency as a waveform graph. GMM MMM HMM

62 32. Many DSOs and GMMs allow capture & transfer of screens & data to a PC. True or False

63 33. Measuring across a fuse or other circuit protection device tells more about its condition than a continuity test. Voltage Drop Voltage Available Voltage Capacitance

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65 34. Some systems, like power seat motors use a PTC as circuit protection. When the current is high, the resistance of the thermistor increases to decrease current or even stop flow. Thermistor Resistor Transistor

66 35. Both manual switches & automatic switches (pressure switch) can be checked, checked for continuity, voltage drop checked or even bypassed with a jumper wire to verify operation. Open Short High Resistance

67 36. Testing of can be done with jumper wires, a volt meter, ohmmeter, or a test light. Relays Relays Relays

68 30 87a a 87

69 A car relay is a electro magnetic switch that uses a small amount of current to control a larger amount of current. How they work is by a wire wound magnetic coil that when excited by a electric current, moves a mechanical spring contact inside the relay, completing a circuit. Car relays are usually controlled by another switch such as your car horn button, headlight switch circuit or power window / door lock switches. Relays are located all over a car, truck, van, suv or hybrid. They are placed in the engine compartment, fuse box or fuse panel, under the dash board or behind door panels and kick panels. Check your owners manual or service manual for exact placement 30 87a 87

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73 The control circuit (GREEN) powers the coil inside the relay, using a small amount of current. It flows from the battery, thru the fuse ( for protection) to a switch, (say, a light switch) then to the coil in the relay, energizing it.

74 The coil, now energized becomes an electromagnet, and attracts the metal strip with the contacts, which closes, providing a secondary heavy current path ( RED ) to the device ( say, the fog lights) Turning off the switch, opens the circuit to the coil, removes current flow, and the electromagnet is no longer a magnet, the secondary path is opened, and the lights extinguish. As the relay turns off, the voltage spike (inductive kick) will take place in the coil & may need a clamping diode to protect the control circuit.

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79 NOTE: In a basic or resistor protection relay, pins 1 and 2 of the micro relays and pins 85 and 86 of the mini relays can be interchanged positive or negative. In a diode protected relay, Mini relays must be pin 85 (+) power, pin 86 ( ) ground / Micro relays must be pin 2 (+) power, pin 1 ( ) ground. Look for a relay diagram or a relay schematic that is printed on the side of the relay to determine.

80 Protection Diode = Clamping Diode, Parallel to Coil for Spike Suppression Current flowing through a relay coil creates a magnetic field which collapses suddenly when the current is turned off. The sudden collapse of the magnetic field induces a brief high voltage across the relay coil that wants to flow in the opposite direction which can cause damage to a ECM, PCM or ICs. A quenching protection diode or suppression resistor allows the induced voltage a path to block and dissipate. This prevents spiked voltage becoming high enough to cause damage to a electronic control module or a IC.

81 Spike Suppression Resistor Located Parallel to Coil Current flowing through a relay coil creates a magnetic field which collapses suddenly when the current is turned off. The sudden collapse of the magnetic field induces a brief high voltage across the relay coil that wants to flow in the opposite direction which can cause damage to a ECM, PCM or ICs. A quenching protection diode or suppression resistor allows the induced voltage a path to block and dissipate. This prevents spiked voltage becoming high enough to cause damage to a electronic control module or a IC.

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86 37. The best way to test a stepped resistor is with an ohmmeter. True or False

87 38. An unpowered can be sweep tested with an ohmmeter, preferably a GMM. Potentiometer Capacitor Transistor

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90 39. The best way to check wiring is to check the across it. Current Voltage Available Voltage Drop

91 40. When troubleshooting, verify the complaint, then use the wiring diagrams & do quick checks of source & ground to narrow the problem down. Voltage Amperage Resistance

92 41. When probing, using too large of an adapter can deform & loosen terminals. Front Back Side

93 42. probing is necessary when tests like voltage drop need to be done on a live circuit. Front Back Side

94 43. If you test wiring by through the insulation, cover the damage to prevent corrosion. Piercing Slicing Dicing

95 44. For circuit diagnosis a diagram is one of the most important sources of information. Wiring Vacuum Symptom

96 45. Connectors and are typically numbered to make location easier. (Cxxx Sxxx Gxxx) Grounds Wires Bulbs

97 46. When tracing a circuit on a schematic, start at the that is not working, find its source, its ground, its switch or control, and the circuit protection. Then get busy with the DMM! This Circuit Has Splices Connectors Grounds Source Component, Consumer, or Load Ground

98 47. Printing out the circuit & using to trace it can help avoid confusion. Black Marker Highlighter Lipstick

99 48. All circuit issues can be boiled down to 1 of 3 things:, & high. Opens, Shorts, High Resistances Fuses, Wiring, Consumers Grounds, Splices, Connectors

100 49. A component with a shorted coil of wire will read than specs or even zero resistance. Greater Less Same

101 50. A fuse never blows without a reason, probably blown due to a to ground. Open Short High Resistance

102 51. High resistance problems are typically caused by that decreases intensity. (amps) Corrosion Solder Electrical Tape

103 52. Many electrical problems can be traced to faulty wiring or. Connections Splices Grounds

104 53. Re routing wires can result in unwanted voltages from electromagnetic fields. Induced Reduced Seduced

105 54. All replacement wires should be the size or larger than the original, never smaller. Same Same Same

106 55. wires (the proper way to connect wires) joins them by melting a lead & tin alloy and allowing it to flow into the joint. 60/40 rosin core solder of a.032 diameter works well. Welding Twisting Soldering

107 56. When soldering near heat sensitive components, use a heat to prevent damage. Shrink Sink Stick

108 57. After crimping & soldering a wire splice, place shrink tubing over the splice, and warm it with a heat gun to protect the joint from elements that could cause corrosion & shorts. Meat Heat Cold

109 58. Wire terminal and release tools prevent connector damage when unlocking terminals. Picks Sticks Tricks