start Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 OBJECTIVES: After studying Chapter 36, the reader should be able to: • • • • Prepare for ASE Electrical/Electronic Systems (A6) certification test content area “A ” (General Electrical/Electronics System Diagnosis) Draw the symbols used on schematics Discuss the various methods that can be use to locate a short circuit List the electrical troubleshooting diagnosis steps Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 KEY TERMS: double-pole, double-throw switch (DPDT) • double-pole, single-throw switch (DPST) gauss gauge • momentary switch normally closed (N.C.) • normally open (N.O.) • poles relay • short circuit • single-pole, double-throw switch (SPDT) • single-pole, single-throw switch (SPST) terminal • throws • tone generator tester wiring schematic Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 WIRING SCHEMATICS Manufacturers’ service manuals include wiring schematics of all the electrical circuits of a vehicle A wiring schematic, called a diagram, shows electrical components and wiring using symbols and lines to represent components and wires A typical wiring schematic may include all of the circuits combined on several large fold-out sheets, or they may be broken down to show individual circuits All circuit schematics or diagrams include the power-side wiring of the circuit and all splices, connectors, electrical components, and ground return paths Gauge and color of wiring are included on most wiring diagrams Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Circuit Information Many wiring schematics include numbers and letters near components and wires that may confuse readers of the schematic Most letters used near or on a wire identify the color or colors of the wire The first color or color abbreviation is the color of the insulation, the second color is the color of the strip or tracer on the base color Chart on Page 370 of your textbook Figure 36–1 The center wire is a solid color wire, meaning that the wire has no other identifying tracer or stripe color The two end wires could be labeled “BRN/WHT,” indicating a brown wire with a white tracer or stripe Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Shown here is a rear side-marker bulb circuit diagram where “.8 ” indicates the metric wire gauge size in square millimeters (mm 2) and “PPL ” indicates a solid purple wire The diagram also shows the color of the wire changes at C210 This stands for “connector #210” and is used for reference purposes, and can vary depending on the manufacturer The color change from purple (PPL) to purple with a white tracer (PPL/WHT) is not important except to know where the wire changes color in the circuit Wire gauge remained the same on both sides of the connection Figure 36–2 Typical section of a wiring diagram Notice that the wire color changes at connection C210 The “.8” represents the metric wire size in square millimeters Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Electrical and electronic symbols used in wiring & circuit diagrams See the chart on Page 371 of your textbook Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Figure 36–3 This figure shows typical electrical and electronic symbols used in automotive wiring and circuit diagrams ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Read The Arrows Wiring diagrams indicate connections by symbols that look like arrows Do not read these “arrows” as pointers showing the direction of current flow Also observe that the power side (positive side) of the circuit is usually the female end of the connector Figure 36–4 In this typical connector, note that the positive terminal is usually a female connector If a connector becomes disconnected, it will be difficult for the circuit to become shorted to ground or to another circuit because the wire is recessed inside the connector Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SCHEMATIC SYMBOLS Schematic drawings replace photos, or line drawings of actual components with a symbol that represents the actual component: Battery The plates of a battery are represented by long and short lines The longer line represents the positive plate of a battery and the shorter line represents the negative plate of the battery Each pair of short and long lines represents one cell of a battery Figure 36–5 The symbol for a battery The positive plate of a battery is represented by the longer line and the negative plate by the shorter line The voltage of the battery is usually stated next to the symbol Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Because each cell of a typical automotive lead-acid battery has 2.1 volts, a battery symbol showing a 12-volt battery should have six pairs of lines However, most symbols simply use two or three pairs of long and short lines and list battery voltage next to the symbol The positive terminal of the battery is indicated with a plus sign (+), representing the positive post of the battery, placed next to the long line of the end cell The negative (ground) terminal is represented by a negative sign (–) and is placed next to the shorter cell line Figure 36–6 The ground symbol on the left represents earth ground The ground symbol on the right represents a chassis ground Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 10 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Gauss Gauge Method A special pulsing circuit breaker (similar to a flasher unit) can be installed in place of the fuse Current will flow through the circuit until the circuit breaker opens the circuit As soon as the circuit breaker opens the circuit, it closes again This on-and-off current flow creates a pulsing magnetic field around the wire carrying the current A Gauss gauge is a handheld meter that responds to weak magnetic fields This pulsing magnetic field will register on the Gauss gauge even through the metal body of the vehicle A needle-type compass can also be used to observe the pulsing magnetic field See Figures 36–33 and 36–34 Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 50 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 36–33 (a) After removing the blown fuse, a pulsing circuit breaker is connected to the terminals of the fuse (b) The circuit breaker causes current to flow, then stop, then flow again, through the circuit up to the point of the short-to-ground By observing the Gauss gauge, the location of the short is indicated near where the needle stops moving due to the magnetic field created by the flow of current through the wire Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 51 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 36–34 A Gauss gauge can be used to determine the location of a short circuit even behind a metal panel A Gauss gauge is used to observe a pulsing magnetic field, which is indicated on the gauge as needle movement Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 52 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Electronic Tone Generator Tester An electronic tone generator tester can be used to locate a short-to-ground or an open circuit Similar to test equipment used to test telephone and cable television lines, a tone generator tester generates a tone that can be heard through a receiver (probe) The tone will be generated while there is a continuous electrical path along the circuit The signal will stop if there is an open (break) or short-to-ground in the circuit The windings in the solenoids and relays will increase the strength of the signal in these locations Figure 36–35 A tone generator-type tester used to locate open circuits and circuits that are shorted-to-ground Included with this tester is a transmitter (tone generator), receiver (probe), and headphones for use in noisy shops See Figures 36–36 and 36–37 Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman Continued 53 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 36–36 To check for a short-to-ground using a tone generator, connect the black transmitter lead to a good chassis ground and the red lead to the load side of the fuse terminal Turn the transmitter on and check for tone signal with the receiver Using a wiring diagram, follow the strongest signal to the short-to-ground There will be no signal beyond the fault Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 54 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Figure 36–37 To check for an open (break), connect the red lead of the tone generator to the load side of the fuse terminal and the black lead to a good chassis ground Turn on the transmitter an then listen for the tone signal with the receiver set in the open position Using a wiring diagram, follow the signal along the circuit until the tone stops, indicating the location of the open Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 55 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Heat or Movement Electrical shorts are commonly caused either by movement, which causes the insulation around the wiring to be worn away, or by heat melting the insulation When checking for a short circuit, first check the wiring that is susceptible to heat, movement, and damage: Heat Wiring near heat sources, such as the exhaust system, cigarette lighter, or generator Wire movement Wiring that moves, such as in areas near the doors, trunk, or hood Damage Wiring subject to mechanical injury, such as in the trunk, where heavy objects can move around and smash or damage wiring This can also occur as a result of an accident or a previous repair Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 56 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Wiggle Test Intermittent electrical problems are common yet difficult to locate To help locate these hard-to-find problems, try operating the circuit and then start wiggling the wires and connections that control the circuit If in doubt where the wiring goes, try moving all the wiring starting at the battery Pay particular attention to wiring running near the battery or the windshield washer container Corrosion can cause wiring to fail, and battery acid fumes and alcohol-based windshield washer fluid can start or contribute to the problem If you notice any change in the operation of the device being tested while wiggling the wiring, look closer in the area you were wiggling until the actual problem is located and corrected Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 57 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 ELECTRICAL TROUBLESHOOTING GUIDE For a device to work, it must have power and ground If there is no power to a device, an open power side (blown fuse, etc.) is indicated If there is power on both sides of a device, an open ground is indicated If a fuse blows immediately, a grounded power-side wire is indicated Most electrical faults result from heat or movement Most noncomputer-controlled devices operate by opening and closing the power side of the circuit (power-side switch) Most computer-controlled devices operate by opening and closing the ground side of the circuit (ground-side switch) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 58 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 STEP-BY-STEP TROUBLESHOOTING PROCEDURE The following procedure has been field tested for many years and provides a step-by-step guide to follow when troubleshooting: Determine the customer concern (complaint) and get as much information as possible from the customer or service advisor a When did the problem start? b Under what conditions does the problem occur? c Have there been any recent repairs to the vehicle which could have created the problem? Verify the customer’s concern by actually observing the fault HINT: Split the circuit help isolate the problem and start at the relay Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 59 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Perform a thorough visual inspection and be sure to check everything that does and does not work Check for technical service bulletins (TSBs) Check the factory service information and follow the troubleshooting procedure a Determine how the circuit works b Determine which part of the circuit is good, based on what works and what does not work c Isolate the problem area Determine the root cause and repair the vehicle Verify the repair and complete the repair order (R.O.) by listing the three C’s (complaint, cause, and correction) Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 60 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 Shocking Experience A customer complained that after driving for a while, he got a static shock whenever the door handle was grabbed when exiting the vehicle The customer thought that there must be an electrical fault and that the shock was coming from the vehicle itself In a way, the shock was caused by the vehicle, but it was not a fault The service technician sprayed the cloth seats and carpet with an antistatic spray and the problem did not reoccur Obviously, a static charge was being created by movement of the driver’s clothing on the seats and discharged when the driver touched the metal door handle Figure 36–38 Antistatic spray can be used to stop customers from being shocked when they touch a metal object like the door handle Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 61 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY Most wiring diagrams include the wire color, circuit number, and wire gauge The number used to identify connectors, grounds, and splices usually indicates where they are located in the vehicle All switches and relays shown on a schematic are shown in their normal position either normally closed (N.C.) or normally open (N.O.) Continued Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 62 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 SUMMARY (cont.) A short-to-voltage affects the power side of the circuit and usually involves more than one circuit A short-to-ground usually causes the fuse to blow and usually affects only one circuit Most electrical faults are a result of heat or movement Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 63 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458 end Automotive Technology: Principles, Diagnosis, and Service, 3rd Edition By James D Halderman 64 ©©2008 2009Pearson PearsonEducation, Education,Inc Inc Pearson PearsonPrentice PrenticeHall Hall- -Upper UpperSaddle SaddleRiver, River,NJ NJ07458 07458