© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Chapter 16 General Electrical System Diagnostics and Service

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Opens – Are breaks in the circuit that stop current flow Shorts – Are unwanted paths for current High Resistance – Occurs when there is unwanted resistance in a circuit Electrical Problems

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Open Circuits Incomplete circuit Loose wires or connectors Broken wires Voltage will be present to the open point No current flow and no voltage drop

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Shorted Circuits A circuit with an unwanted path for current to flow Can cause uncontrolled high current flow Caused by damaged insulation, loose wires and connections, and improper wiring

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Short to Ground

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Shorted Circuits (Cont.) Short to ground before the load should open circuit protection – Reduced circuit resistance from bypassing the load increases the current flow Short to power can cause unwanted circuit operation

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High-Resistance Circuits Unwanted resistance in a circuit Higher resistance decreases current flow Corrosion at connectors is common The corrosion becomes an additional load and creates a voltage drop

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. The added resistance in figure B reduces the voltage available for the light

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electrical Wiring Diagrams Also called schematics Does not show location or actual appearance of components Symbols are used to represent components

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.

Electrical Diagrams (Cont.) Diagram may illustrate one system or one part of a complex system

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Connector and Terminals Connectors are often plastic and can contain one or many terminals Terminals are located inside the connector Connectors and terminals are male or female

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electrical Testing Tools Multimeter – Measures the voltage available at any point in the circuit – Also measures resistance and current – May perform other test functions

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Lab Scopes – Fast acting multimeters that measure and display voltages within a specific time frame – The voltage appears as a waveform or trace – Upward movement means increasing voltage Electrical Testing Tools (Cont.)

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Scan Tools Plugs into vehicle diagnostic connector Retrieves fault codes Displays sensor data Access freeze frames

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electrical Testing Tools (Cont.) Circuit Testers (Test Lights) – Are used to identify opens or shorts – Also used to show current flow – Can be non-powered or powered

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Electrical Testing Tools (Cont.) Other Test Equipment – Jumper wires are used to bypass a switch or connector – Computer memory savers are installed when the vehicle battery needs to be disconnected

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Multimeters Digital multimeters (DMM) most common Also called digital volt/ohmmeters (DVOM) Analog meters should not be used on electronic equipment Meters used on HV vehicles should be rated Category III (CAT III)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Multimeters Display Area Range Selectors – Many meters have auto range ability Mode Selectors – AC volts, DC volts, Ohms, Amps, plus other features Jacks/Test Leads

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Voltage A DMM can measure source voltage, available voltage, and voltage drop Voltage is measured with the meter in parallel to the circuit

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Available Voltage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing for Voltage Drop Voltage drop must be tested with the circuit energized Identifies unwanted resistance The voltage indicated is the amount of voltage used between where the red lead is connected and where the black lead is connected

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. 0.1 volts per connection is acceptable in non-computerized circuits volts (50 millivolts) per connection is acceptable in computerized circuits Excessive voltage drop is an indication of high resistance Testing for Voltage Drop (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Voltage Drop

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Describe the difference between measuring voltage and measuring voltage drop.

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring AC Voltage Can be displayed as root mean square (RMS) and average responding Both methods will display the same for a true sine wave RMS meters convert the AC signal into a comparable DC voltage signal Average responding displays the average voltage peak

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Current Tests the circuit under load Low current indicates high resistance DMM placed in series into the circuit Check the meter rating before attempting to measure current flow

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Inductive Current Probes DMM usually limited to measuring 10A To read higher amperages, an inductive current probe or clamp is used

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Measuring Resistance Tested with circuit off and disconnected Attempting to measure resistance on a powered circuit may damage the meter Resistance can be checked and compared to specifications Can be caused by loose, damaged, or dirty connections

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Continuity Tests Many DMMs have an audible alert when continuity is present Can be used when testing for an intermittent problem Connect the DMM and move wiring and note when the beeping stops

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. MIN/MAX Readings Some DMMs have a MIN MAX function Displays minimum, maximum, and average voltage recorded during testing Can be used to check for radio frequency interference (RFI)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Other Measurements Duty Cycle – measured as a percentage of a devices on time Pulse Width – measured in milliseconds (ms), the amount of time something is on Frequency – measured in Hertz, how many times per second a signal occurs Temperature – determined with a temperature probe

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Duty Cycle

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Pulse Width

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Frequency

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. DMM Safety Guidelines Use only as designed to be used Never use a damaged meter Ensure battery is secured and enclosed Inspect leads and replace if damaged Never apply more than rated voltage Use proper connections, mode, and ranges Turn circuit off before measuring current

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Lab Scopes Displays any change in voltage as it occurs Screen divided into divisions of time and voltage Time and voltage displays can be adjusted

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Analog vs. Digital Scopes Analog scopes display in real time Digital scopes, or digital storage oscilloscopes (DSOs) convert signals into digital information Both can be dual trace Some DSOs have four channels

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Analog Scope

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Waveforms Represents voltage over time Any change in amplitude indicates a change in voltage Scopes can display AC and DC voltage

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Select the best voltage and time base setting – If the time base setting is too long and the voltage setting is too high, the waveform is too small to read – If the time base setting is too short and the voltage setting is too low, the waveform is too large for the screen Scope Controls

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Select the nearest voltage setting higher than the expected voltage Start at the highest time base and move down until the proper pattern appears Select the proper trigger setting for the signal being tested Scope Controls (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Graphing Multimeters (GMM) Displays voltage, resistance, current, and frequency as a waveform May included a signal and data recorder, component tests, glitch capture, and audible alarms Some include a library of known-good signals

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Graphing Multimeters (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Transferring Data to a PC Many DSOs and GMMs allow for data transfer to a PC Allows for a library of waveforms and other data

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing Basic Electrical Components All electrical components can fail Think about what the component is supposed to do then figure out how to test the component Often, removing and testing on a bench is the best way to test

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Ohmmeter – Tests for continuity across the protection device Test light or voltmeter – Checks for voltage at both sides of the protection device – Checks for voltage drop across the protection device Checking Circuit Protection Devices

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Fuse Testing

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wire with special insulation The wire melts to open the circuit Fuse Links

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Maxi-Fuses – Replacing fuse links – Easier to replace Circuit Breakers – One type resets by removing power from circuit – Other type resets by pressing a button Thermistors – High current flow increase resistance Circuit Protection Devices

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Switches Disconnect switch and check continuity between terminals

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Never use a test light to test a computer- controlled relay Verify the presence of voltage at both the control and the controlled side of the relay Verify the continuity of the relay coil Just because the relay “clicks” doesn’t mean it is good Relay Testing Tips

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Explain how to use a DMM to test a fuse.

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Stepped Resistors Test resistance or voltage after each resistor

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Variable Resistors Check resistance or output voltage Both resistance and voltage changes should be smooth and consistent during sweep Lab scopes can show very small defects or glitches

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wiring Check insulation – Broken, frayed, or damaged insulation can cause short circuits Inspect ground connections Perform a voltage drop test on the wire

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Damaged Wiring

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Printed Circuits Flexible printed circuit boards are not serviceable Never touch board surface Cleaned with commercial cleaner or by lightly rubbing pencil eraser across surface Easily damaged when replacing bulbs

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Gather information about the problem Verify the customer’s complaint Define the problem and when it occurs Research all information to determine possible causes Isolate the problem Troubleshooting Circuits

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Troubleshooting Circuits (Cont.) Continue testing to pinpoint the cause of the problem Locate and repair the problem Verify the repair

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Troubleshooting Logic Remember three types of circuit problems Perform voltage checks Take measurements at a connector Use adaptors to front and back probe connectors

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Wiring Diagrams One of the most important resources Shows relationships of circuits They illustrate: – Wires by number or color coding – Wire cross-section size – Ground connections – Wire connection points

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Using Wiring Diagrams (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Diagrams show: – Reference wire continuation – Location of splices – Terminal designations – Component symbols – Switches – Fuse designations – Relay information – Circuit continuation Using Wiring Diagrams (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Getting the Right Diagram Should be for the exact year, make, and model Refer to the VIN May have system specific diagrams Some vehicles have only total vehicle diagrams

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Tracing a Circuit Identify components, connectors, and wires related to diagnosis Trace power through the circuit with highlighters Identify power, ground, loads, and controls

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Tracing a Circuit (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. If possible, start testing at the load component Check for voltage on the power side of the component – If voltage is present, check the ground side – If voltage is not present, test all connections working toward the battery – If voltage is present at a connection, the open is between it and the previously tested point Testing for Opens

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing for Opens (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. If the power side of the circuit tests good, test the ground side – Use a jumper wire to bypass the ground side of the circuit, and if the component works, check all ground side connections If both the power and ground circuits test good, the load component is open Testing for Opens (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check Technician A says an open ground can cause a component not to operate. Technician B says an open ground can cause a reading of battery voltage on the components ground wire. Who is correct?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Use an ohmmeter to check resistance of the circuit If there is a short, the resistance will be less than specified If the short is between two circuits, components may operate when not intended Testing for Shorts

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing for Shorts (Cont.)

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Testing for Unwanted Resistance Typically caused by corrosion, loose or poor connections, frayed or damaged wires Check voltage drop across the load Check sections of the circuit to find the unwanted resistance

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Common Causes of Wiring Problems Corroded terminals Loose terminals Frayed, broken, or oil- soaked wires Faulty insulation

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Type of repair required Ease of access to the damaged area Type of conductor Size of wire Circuit requirements Manufacturer’s recommendations Wire Repair Considerations

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Wrapping with electrical tape or tubing – Designed to insulate one circuit from another Solderless connectors – Designed to be used in areas not subject to weather, dirt, corrosion, or movement Soldering – The best way to splice copper wires Wire Repair

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Identify the type of terminal and locking clips Remove the terminal Install and solder new terminal Reinstall the terminal into the connector Replacing a Terminal

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part. Knowledge Check What type of solder should be used on electrical wiring?

© 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied, duplicated, or posted to a publicly accessible website, in whole or in part.