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Automotive Electrical SystemsAutomotive Electrical Systems

R. BortignonR. Bortignon

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Electrical CircuitsElectrical Circuits

Contain 4 main parts…Contain 4 main parts…

1. Power source1. Power source batterybattery alternatoralternator

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LoadLoad2. The2. The loadload in a circuit is the part that does thein a circuit is the part that does the workwork

load will always have some resistanceload will always have some resistance this resistance can be measuredthis resistance can be measured

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ControlControl3. The 3. The controlcontrol is what turns the load on or off… is what turns the load on or off… opens & closes the circuitopens & closes the circuit may be installed on the ground side or the power side of circuitmay be installed on the ground side or the power side of circuit

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PathPath

4. The path are the 4. The path are the wireswires that connect the battery & alternator to the control and that connect the battery & alternator to the control and load devices in a circuitload devices in a circuit frame/body of the vehicle is a path for the ground circuitframe/body of the vehicle is a path for the ground circuit

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Circuit ProtectionCircuit Protection

• to protect the vehicle’s electrical system from excessive current flow, fuses are usedto protect the vehicle’s electrical system from excessive current flow, fuses are used

fuses open the circuit if current (amperage) levels exceed a predetermined levelfuses open the circuit if current (amperage) levels exceed a predetermined level

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Types of FusesTypes of Fuses

• cartridge fusescartridge fuses

• blade type fusesblade type fuses mini sizemini size standard sizestandard size maxi sizemaxi size mega fusemega fuse

• ceramic disc fusesceramic disc fuses see info on next slidesee info on next slide

replace fuses with correct amperage rating!!!replace fuses with correct amperage rating!!!

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Positive Temperature Coefficient FusesPositive Temperature Coefficient Fuses

PTC fuse technology utilizes a polymer-based material to protect electrical circuits from excessive PTC fuse technology utilizes a polymer-based material to protect electrical circuits from excessive

current. current.

During normal operation, numerous carbon paths within the polymer allow the device to conduct During normal operation, numerous carbon paths within the polymer allow the device to conduct

electricity. electricity.

As current through the PTC fuse reaches its rated threshold, the polymer material begins to heat As current through the PTC fuse reaches its rated threshold, the polymer material begins to heat

causing the polymer to expand. causing the polymer to expand.

The resulting expansion breaks the carbon chains to reduce the current through the circuit to a small The resulting expansion breaks the carbon chains to reduce the current through the circuit to a small

leakage current. leakage current.

The increased resistance in this resettable fuse works to protect circuitry by limiting potentially The increased resistance in this resettable fuse works to protect circuitry by limiting potentially

damaging current. damaging current.

When the fault (over-current) is removed from the circuit, When the fault (over-current) is removed from the circuit, the PTC fuse will reset itselfthe PTC fuse will reset itself thereby thereby

allowing current to flow through the circuit again.allowing current to flow through the circuit again.

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• many older vehicles use glass cartridge fusesmany older vehicles use glass cartridge fuses

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Fuse Panel LocationsFuse Panel Locations

• can be located…can be located… under left side of instrument panelunder left side of instrument panel in the engine compartmentin the engine compartment many vehicles have fuse panels in many vehicles have fuse panels in both locationsboth locations

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Fusible LinksFusible Links

• special wire that breaks & opens a circuit when overloadedspecial wire that breaks & opens a circuit when overloaded

• insulation bubbles, melts & opens to expose wireinsulation bubbles, melts & opens to expose wire

• usually connected near the battery & feeds the fuse box(es)usually connected near the battery & feeds the fuse box(es)

• must be replaced with correct ratingmust be replaced with correct rating

• not all vehicles use fusible linksnot all vehicles use fusible links

modern vehicles use maxi fuses instead of fusible linksmodern vehicles use maxi fuses instead of fusible links

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Circuit BreakersCircuit Breakers

• some circuits such as power windows & power seats use some circuits such as power windows & power seats use circuit breakerscircuit breakers• circuit breakers reset themselves when current levels are back to normal circuit breakers reset themselves when current levels are back to normal

(do not need to be replaced like fuses)(do not need to be replaced like fuses)

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Electrical System Service & Testing…Electrical System Service & Testing…

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Testing FusesTesting Fuses

• 1) test with an ohmmeter set on the low scale1) test with an ohmmeter set on the low scale should have low/no resistanceshould have low/no resistance be careful checking fuses visuallybe careful checking fuses visually

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Testing FusesTesting Fuses• 2) test with a test light2) test with a test light the key may have to be in the on positionthe key may have to be in the on position the control/switch for the circuit may have to be onthe control/switch for the circuit may have to be on

• test light should light up test light should light up on both sideson both sides of the fuse of the fuse• if only one side lights up – fuse is openif only one side lights up – fuse is open• if neither side lights up – power is not reaching the fuseif neither side lights up – power is not reaching the fuse

1

3

2

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RelaysRelays• use a low current signal to activate a high current circuituse a low current signal to activate a high current circuit• relay coil draws 150mArelay coil draws 150mA• contacts can conduct 30-50ampscontacts can conduct 30-50amps

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Electrical Faults – High ResistanceElectrical Faults – High Resistance

• circuit may not work at allcircuit may not work at all• circuit may be dim or work poorly / slowlycircuit may be dim or work poorly / slowly

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Electrical Faults – Low ResistanceElectrical Faults – Low Resistance

the load’s resistance is partially or totally bypassedthe load’s resistance is partially or totally bypassed often referred to as a often referred to as a shortshort causes higher than normal current flowcauses higher than normal current flow usually causes fuse to open the circuitusually causes fuse to open the circuit

frayed wire/bare insulation

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Light BulbsLight Bulbs

• bulbs can be single or double filamentbulbs can be single or double filament double filament = brake light & park lightdouble filament = brake light & park light note the offset indexing pins & note the offset indexing pins & 2 contacts2 contacts

newer style bulbs newer style bulbs do notdo not require indexing require indexing

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Testing BulbsTesting Bulbs• often “blown” bulbs are easily seen during a visual inspectionoften “blown” bulbs are easily seen during a visual inspection• sometimes a DVOM will verify the problemsometimes a DVOM will verify the problem

use low resistance settinguse low resistance setting polarity doesn’t matterpolarity doesn’t matter most bulbs will be ≈ 3Ω to 10Ωmost bulbs will be ≈ 3Ω to 10Ω you are looking for…you are looking for…

shorts (low/no Ω)shorts (low/no Ω) opens (high Ω)opens (high Ω)

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Testing HeadlampsTesting Headlamps

• older style sealed beamsolder style sealed beams

• newer halogen, xenon bulbsnewer halogen, xenon bulbs do not touch the quartz when replacing these!do not touch the quartz when replacing these!

• 1 connector is for ground – check for continuity to ground1 connector is for ground – check for continuity to ground• 22ndnd connector is for hi beam – check for voltage connector is for hi beam – check for voltage• 33rdrd connector is low beam – check for voltage connector is low beam – check for voltage

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Turn SignalsTurn Signals• blinking function of the turn signals is controlled by blinking function of the turn signals is controlled by turn signal flasherturn signal flasher• may have 1 that controls turn signals & 4 way flashermay have 1 that controls turn signals & 4 way flasher• or 2 separate unitsor 2 separate units• located in fuse box or under the left side of the dashlocated in fuse box or under the left side of the dash

if if one sideone side flashes abnormally fast – check for faulty bulb on that side of the vehicle flashes abnormally fast – check for faulty bulb on that side of the vehicle if if both sidesboth sides flash incorrectly, the flasher unit may be faulty flash incorrectly, the flasher unit may be faulty

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Reading Wiring DiagramsReading Wiring Diagrams

• wire colors – jacket color followed by stripe colorwire colors – jacket color followed by stripe color• connectors – identification numbersconnectors – identification numbers• usually +usually + side of the circuit up top & ground at the bottomside of the circuit up top & ground at the bottom• ground number & locationsground number & locations

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Using Using Component LocationComponent Location Function Function

• component locator can be used to find connectors, relays, grounds, modules etc.component locator can be used to find connectors, relays, grounds, modules etc.• access access electricalelectrical, then , then component locationcomponent location in Mitchell in Mitchell

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Starter CircuitStarter Circuit• terminal “B” (battery) is live at all timesterminal “B” (battery) is live at all times• terminal “S” (start) feeds power only when the key is in the starting positionterminal “S” (start) feeds power only when the key is in the starting position

““S” terminal will have a neutral safety switch in series for an automatic transmission equipped S” terminal will have a neutral safety switch in series for an automatic transmission equipped carcar

““S” terminal can also have a clutch safety switch in series for a manual transmission equipped carS” terminal can also have a clutch safety switch in series for a manual transmission equipped car ““S” terminal may have remote starter switch or alarm disabling feature tied into itS” terminal may have remote starter switch or alarm disabling feature tied into it

• terminal “M” (motor) has power during cranking onlyterminal “M” (motor) has power during cranking only

B

S

M

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Starter SolenoidStarter Solenoid

• serves same purpose as a relayserves same purpose as a relay• is usually mounted directly on the starter motoris usually mounted directly on the starter motor• on Fords, it is mounted remotely on the inner fenderon Fords, it is mounted remotely on the inner fender

Voltage Drop TestVoltage Drop Test

• determines if too much voltage is being lost to poor connections determines if too much voltage is being lost to poor connections • voltmeter is set to low voltage scale (0-2v)voltmeter is set to low voltage scale (0-2v)• meter leads are placed across a connection (circuit must be turned on during testing)meter leads are placed across a connection (circuit must be turned on during testing)• there should not be more than .1v loss per connectionthere should not be more than .1v loss per connection• both the positive and ground circuits can be tested this wayboth the positive and ground circuits can be tested this way

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Hey Mr. B can I install…Hey Mr. B can I install…

• the next 5 slides are helpful when adding electrical accessories to a vehiclethe next 5 slides are helpful when adding electrical accessories to a vehicle

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Adding AccessoriesAdding Accessories

• you and your students need to carefully consider what’s needed when adding amplifiers, you and your students need to carefully consider what’s needed when adding amplifiers, driving lights etc.driving lights etc.

• add a relay to an existing circuit so you don’t overload the original circuitadd a relay to an existing circuit so you don’t overload the original circuit

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Adding Fuses to Add-on AccessoriesAdding Fuses to Add-on Accessories

• when adding additional equipment, add a relay to power the circuitwhen adding additional equipment, add a relay to power the circuit

• calculate the required fuse amperagecalculate the required fuse amperage eg: 2 fog lights 4Ω eacheg: 2 fog lights 4Ω each amperage = 12 volts ÷ 4Ω = 3 amps through each lightamperage = 12 volts ÷ 4Ω = 3 amps through each light 3 amps X 2 lights = 6 amps total3 amps X 2 lights = 6 amps total

• 6 amps flowing through circuit6 amps flowing through circuit

• multiply this by 1.5 to allow for any voltage surgesmultiply this by 1.5 to allow for any voltage surges

• 6 amps X 1.5 = 6 amps X 1.5 = install a 9 amp fuseinstall a 9 amp fuse

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Hey Mr. B, do you have any wire?Hey Mr. B, do you have any wire?

determining wire gauge size for add-on circuits…determining wire gauge size for add-on circuits… use a wire gauge tableuse a wire gauge table always better to use a larger gauge size than is requiredalways better to use a larger gauge size than is required

3' 5' 7' 10' 15' 20' 25'

up to 5 amps 18 18 18 18 18 18 18

6 18 18 18 18 18 18 16

7 18 18 18 18 18 18 16

8 18 18 18 18 18 16 16

10 18 18 18 18 16 16 16

11 18 18 18 18 16 16 14

12 18 18 18 18 16 16 14

15 18 18 18 18 14 14 12

18 18 18 16 16 14 14 12

20 18 18 16 16 14 12 10

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Wiring Repair TipsWiring Repair Tips• use grommets & loom to protect wires against abrasionuse grommets & loom to protect wires against abrasion• crimp & solder, then heat shrinkcrimp & solder, then heat shrink• don’t rely on crimp onlydon’t rely on crimp only• on air bag systems & circuits to/from computer modules, follow manufacturer’s specific on air bag systems & circuits to/from computer modules, follow manufacturer’s specific

repair instructionsrepair instructions

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ISO 4 pin & 5 pin relay pin-outsISO 4 pin & 5 pin relay pin-outs…for your reference…for your reference

4 pin relay

5 pin relay