FIGURE 23-1 A thermoelectric fuel gauge has 5 volts coming from the instrument voltage regulator (IVR). The IVR is shared by all other dash instruments. Electronic gauges use the same sensor (sending unit) but use electronic circuits to control needle movement or digital display.

FIGURE 23-2 Instrument voltage regulator FIGURE 23-2 Instrument voltage regulator. Vibrating points maintain current through the instrument at 5 volts. The radio choke prevents radio interference created by the pulsing current low.

FIGURE 23-3 Electromagnetic fuel gauge wiring FIGURE 23-3 Electromagnetic fuel gauge wiring. If the sensor wire is unplugged and grounded, the needle should point to “E” (empty). If the sensor wire is unplugged and held away from ground, the needle should point to “F” (full).

FIGURE 23-4 Many vehicles use a computer display for certain functions including trip computers, radio, clock, and air conditioning. This vehicle is not moving and yet the engine is running, so the fuel economy is zero.

FIGURE 23-5 The ground for the “check oil” indicator lamp is controlled by the electronic low-oil buffer. Even though this buffer is connected to an oil level sensor, the buffer also takes into consideration the amount of time the engine has been stopped and the temperature of the engine. The only way to properly diagnose a problem with this circuit is to use the procedures specified by the vehicle manufacturer. Besides, only the engineer that designed the circuit knows for sure how it is supposed to work.

FIGURE 23-6 A typical head-up display showing zero miles per hour, which is actually projected on the windshield from the head-up display in the dash.

FIGURE 23-7 The dash-mounted control for the head-up display on this Cadillac allows the driver to move the image up and down on the windshield for best viewing.

FIGURE 23-8 A typical HUD unit.

FIGURE 23-9 A night vision camera in the front of a Cadillac.

FIGURE 23-10 This symbol is used to represent a charging circuit problem.

FIGURE 23-11 This oil pressure grounding switch (sending unit) has a fixed contact connected to ground and a contact that is moved by the pressure sensitive diaphragm.

FIGURE 23-12 A typical oil pressure sending unit provides a varying amount of resistance as engine oil pressure changes.

FIGURE 23-13 A Ford oil pressure sending unit FIGURE 23-13 A Ford oil pressure sending unit. Most oil pressure sending units are located near the oil filter and are threaded into an oil gallery.

FIGURE 23-14 Temperature grounding switches expose a bimetallic strip to engine coolant temperature to light a high-temperature lamp or both high- and low-temperature warning lamps.

FIGURE 23-15 Typical red brake warning lamp.

FIGURE 23-16 Typical brake warning light switch located on or near the master brake cylinder.

FIGURE 23-17 The red brake warning lamp can be turned on if the brake fluid level is low.

FIGURE 23-18 (a) Symbol and line drawing of a typical light emitting diode (LED). (b) Grouped in seven segments, this array is called a seven segment LED display with a common anode (positive connection). The dash computer toggles the cathode (negative) side of each individual segment to display numbers and letters. (c) When all segments are turned on, the number 8 is displayed.

FIGURE 23-19 A typical navigation system FIGURE 23-19 A typical navigation system. This Acura system incorporates some of the climate control functions as well as the trip information on the display. This particular unit uses a DVD unit in the trunk along with a global positioning satellite (GPS) to display a map and your exact location for the entire country.

FIGURE 23-20a View of the vehicle dash with the instrument cluster removed. Sometimes the dash instruments can be serviced by removing the padded dash cover (crashpad) to gain access to the rear of the dash.

FIGURE 23-20b The front view of the electronic analog dash display.

FIGURE 23-20c The rear view of the dash display showing that there are a few bulbs that can be serviced, but otherwise the unit is serviced as an assembly.

FIGURE 23-21 Typical ignition switch positions FIGURE 23-21 Typical ignition switch positions. Notice the bulb check position between on (run) and start.

FIGURE 23-22 Many newer vehicles place the ignition switch on the dash and incorporate antitheft controls. Note the location of the accessory position.

FIGURE 23-23 Permanent magnet (PM) generator vehicle speed sensor FIGURE 23-23 Permanent magnet (PM) generator vehicle speed sensor. The unit is usually driven by a gear on the output section of the transmission or transaxle.

FIGURE 23-24 Some vehicles that use a PM generator for a vehicle speed sensor use a stepper motor to drive a mechanical odometer. The stepper motor receives a signal (pulses) from the vehicle computer and rotates in “steps” corresponding to the distance to the distance traveled.

FIGURE 23-25 A typical fuel pump and fuel-level gauge module FIGURE 23-25 A typical fuel pump and fuel-level gauge module. The float moves against a resistor and changes the resistance of the circuit with the fuel level.

FIGURE 23-26a A Ford dash display with the key on, engine off.

FIGURE 23-26b As soon as the engine starts, the oil pressure gauge goes immediately to the midpoint on the gauge. This seems stranger to some vehicle owners.

FIGURE 23-27 A typical magnetic and pressure gauge circuit FIGURE 23-27 A typical magnetic and pressure gauge circuit. Notice that the oil pressure gauge reading depends on the resistance of the sensor. The lower the resistance, the higher the oil pressure on most Ford vehicles.

FIGURE 23-28 When the oil pressure exceeds 4. 5 to 7 FIGURE 23-28 When the oil pressure exceeds 4.5 to 7.5 psi, the oil pressure switch closes and the meter reads in about the middle of its range due to the fixed 20 ohm resistor in the meter circuit.

FIGURE 23-29 Global positioning systems use 24 satellites in high earth orbit whose signals are picked up by navigation systems. The navigation system computer then calculates the location based on the position of the satellite overhead.

FIGURE 23-30 The navigation control unit is located in the trunk of this Acura.

FIGURE 23-31 A typical navigation display showing various options FIGURE 23-31 A typical navigation display showing various options. Some systems do not allow access to these functions if the vehicle is in gear and/or moving.

FIGURE 23-32 A screen display of a navigation system that is unable to acquire usable signals from GPS satellites.

FIGURE 23-33 The three-button OnStar control on the inside rearview mirror. The left button (telephone handset icon) indicates hands-free cellular call. The center button contacts an OnStar advisor and the right emergency button requests that help be sent to the vehicle’s location.

FIGURE 23-34 A typical view displayed on the navigation screen from the backup camera.

FIGURE 23-35 A typical fisheye-type backup camera usually located near the center on the rear of the vehicle near the license plate.

FIGURE 23-36 A typical backup sensor display located above the rear window inside the vehicle. The warning lights are visible in the inside rearview mirror.

FIGURE 23-37 The small round buttons in the rear bumper are ultrasonic sensors used to sense distance to an object.