INSTALLATION KNOWLEDGE & TECHNIQUE
SAMPLE WIRING CODES
Yellow...Battery (+) Black...Ground Red ...Ignition (+) White/Blue ...Illumination (+) Orange/White...Reverse Lights (+)
Green/White...Vehicle Speed Sense (VSS)
In general, the basic connections for power, ground, ignition and illumination should be very straightforward.
■ The reverse light input is a necessary connection. The navigation unit must know when the vehicle is driving in reverse, so it can compensate when determining the precise location of the vehicle.
■ It can typically be found at the transmission switch, the main wire harness that runs to the tail lights or at the reverse light itself.
The most difficult wire to find will be the VSS wire.
■ Some manufacturers, have a special Application Support team that helps installers locate the VSS wire.
Caution: Some older vehicles may not have VSS wires. Under those circum-stances, you must install a speed pulse generator onto the speedometer cable.
VEHICLE SPEED SENSOR TESTING AND VERIFICATION
Once the Vehicle Speed Sensor (VSS) has been installed, you have to test to make sure it is functioning, and then verify its accuracy. There are two types of Vehicle Speed Sensors:
1 Analog 2 Digital Analog VSS
NOTE: If you’re working with an analog VSS, DO NOT hook up the analog speed pulse wire to the navigation system before undergoing the initialization process.
Analog speed pulse is measured as AC voltage with reference to chassis ground.
■ Due to varying AC voltages and frequencies, the only accurate way to ver-ify an analog speed pulse is to use an oscilloscope.
■ If you do not have access to an oscilloscope, verify that the wire does not have a positive DC voltage by using your digital multimeter.
■ Next, set your digital multimeter to AC voltage at the 30-volt range or on auto-range.
■ Connect the black lead of the multimeter to chassis ground.
■ Probe the speed pulse wire with the red lead.
■ The meter should read zero volts.
■ Start the car and drive slowly (you should have someone riding with you to read the multimeter while you drive).
Margin Notes
The meter should slowly begin to show an increase in voltage.
■ At slower speeds, the voltage should be approximately 2 - 5 volts AC.
■ As vehicle speed increases, AC voltage will increase.
■ Maximum AC voltage should be somewhere around 5 - 8 volts at 60 mph.
Do not confuse this process with checking the tachometer wire. The tachometer wire increases voltage with the engine’s RPM. The speed pulse wire increases volt-age with the vehicle's actual speed.
After verifying the analog speed pulse wire, you must follow certain procedures to initialize the navigation system to accept an analog speed pulse prior to attaching the wire to the system.
■ Check the manufacturer’s installation instructions for the proper procedures.
Digital VSS
To test and verify a digital VSS, you will need a digital multimeter set to DC Volts at the 30-volt range or on auto-range.
■ Be sure to question the customer so you understand the powertrain lay-out of the vehicle.
■ For front-wheel drive, jack up only one of the front two wheels.
■ For rear-wheel drive, jack up only one of the rear wheels.
■ For all-wheel drive vehicles, you will need to jack up all of the drive wheels (if you cannot switch to 100% rear-wheel drive or 100% front-wheel drive).
■ For 4-wheel drive vehicles that drive only the rear wheels when in 2-wheel drive mode, jack up only one of the rear wheels.
■ For vehicles with a locking differential, you will need to jack up both (or all) of the drive wheels.
■ Be sure to block the remaining wheels to prevent the vehicle from rolling.
■ Connect the Black lead of the multimeter to chassis ground.
■ Probe the speed pulse wire with the Red lead.
■ Turn the ignition key to the “ON” position, but do not start the vehicle.
■ Read the multimeter.
It should show zero volts (off) or a voltage ranging from 5 - 12 volts (on).
■ The voltage range will differ depending upon the vehicle, however it will not fluctuate.
Margin Notes
■ Rotate the tire slowly.
■ The voltmeter should change state between zero volts (off) and 5 - 12 volts (on) or vice-versa within 2-3 rotations of the tire.
That is all you have to do to verify the digital speed pulse.
TESTING THE SYSTEM
Unlike your typical installation, a navigation system is not fully functional the first time you switch it on. For example, you have to allow the ECU time to get “in sync” with the GPS satellites.
Follow these guidelines:
■ Park the vehicle in an area outside where the GPS antenna has good reception.
■ Make sure the vehicle is away from tall buildings or trees.
■ Turn on the unit.
■ This process takes between 10 and 30 minutes while the system receives the GPS data and finds the approximate vehicle location.
■ Once the unit “wakes up,” typically a disclaimer screen will appear.
■ Press the “ENTER” button.
■ The map screen should appear.
■ In some instances, the vehicle icon may appear on a blank map screen (no roads are illustrated) – this condition is normal.
■ Somewhere on the screen will be a GPS signal icon (it should be in the shape of a satellite).
■ Once the unit receives the GPS data, the GPS icon will change (in some instances, it will change color – from dark gray [no reception], to light blue [minimum reception], to yellow [maximum reception]).
The vehicle icon should now be visible on the map, and the monitor should show the approximate vehicle location.
Don’t worry if the map position is a block or so away from your actual position – the system will correct itself as you drive.
These are only basic guideline for installation. For further guidelines consult the individual GPS manufacturer.
Navigation Systems can be studied in greater depth in the MECP First Class Study Guide.
Margin Notes
SAMPLE TEST QUESTIONS
1 At what frequency is the human ear most sensitive?
A 25 Hz to 35 Hz.
B 100 Hz to 250 Hz.
C 1000 Hz to 2000 Hz.
D 15000 Hz to 20000 Hz.
2 What is sympathetic vibration?
A Noises made by processors.
B The natural resonance of an object.
C Distortion.
D Ignition noise.
3 An audio signal is an electrical representation of what?
A Sound Wave.
B Octave.
C Potentiometer.
D Inductance.
4 Destructive interference refers to two speakers whose sound waves are work-ing against each other and our out of phase by:
A 45º degrees.
B 90º degrees.
C 180º degrees.
D 270º degrees.
E 360º degrees.
5 A Magnetic Reed Switch, also called a magnetic proximity switch:
A Uses magnetic force to cause a set of contacts to connect.
B Uses kinetic energy to open and close a set of contacts.
C Has input for multiple switch triggers.
D Can replace the use of a relay.
6 The most common used device to interrupt a vehicle’s starter is a:
A Electronic switching capacitor.
B Heavy duty diode.
C Electromagnetic switch.
D Pulse timer.
Margin Notes
7 Is an impact sensor the best device to detect breaking glass during a break in attempt?
A True B False
8 A “pulse” or universal timer can be used to:
A Remove unwanted EMI from you security system.
B Add a pulsed output for alternating flashing parking lights.
C Convert a momentary duration pulse into a longer or shorter duration signal.
D Reverse the pulse from negative to positive for door triggers.
9 A glass mount antenna will transmit and receive best:
A When mounted over two defogger grids.
B When it is mounted over an FM antenna grid.
C When mounted between or above the defogger grids.
D When place at a 45º degree angle to the ground plane.
10 Extending the length of the RG 58 coax cable supplied by the manufacture (normally 12-15 feet) can result in as much as 3 dB of signal loss.
A True B False
11 The small holes on the side of the hands free microphone are commonly used for:
A Decoration.
B Noise canceling.
C The mounting clip.
D Have no specific purpose.
12 Painting cellular antenna mast with car paint can typically cause up to 1 dB of loss.
A True B False
Margin Notes
13 Which of the following materials will not attenuate the signal from a GPS antenna:
A Metallic window tint.
B Line defrosters.
C Electrically heated windshields.
D Factory pigment tinted glass.
14 The best choice of mounting position for the GPS antenna is:
A Under the trunk lid.
B Under the hood.
C Under the headliner.
D On the rear deck or dash.
E On the center console.
15 The length of antenna cable on a GPS receiver is;
A Unmatched.
B Preset.
C Random.
D Uncorrelated.
16 A true VSS signal will vary in proportion with;
A Engine temperature.
B Engine RPM.
C Ignition voltage.
D Battery voltage.
E Vehicle speed.
Answers
1 C, 2 B, 3 A, 4 C, 5 A, 6 C, 7 B, 8 C, 9 C, 10 A 11 B 12 A 13 D 14 D 15 B 16 F
Margin Notes