Instrument Cluster

The instrument cluster performs a display prove-out to verify that all warning/indicator lamps and monitored Systems are functioning properly. When the ignition switch is in the ON position with the engine off, the following indicators will illuminate:
- CHECK ENGINE/Malfunction Indicator Lamp (MIL).
- CHECK GAGE warning indicator.
- Charge system indicator.
- Anti-lock Brake (ABS) warning indicator.
- Safety belt warning indicator (60 second prove out).
- Air bag indicator.

Printed Circuit
The instrument cluster printed circuit is a flexible circuit that supplies power and ground to the instrument cluster indicators and gauges. It is constructed of copper foil bonded to a polyester base film (usually referred to as Mylar).

The flexible circuit is mounted to the instrument cluster housing and, due to its location, cannot be easily tested or inspected in the vehicle. This makes the flexible circuit vulnerable to darnage when a probe is used for in-vehicle testing because the probe can pierce the printed circuit or, in some cases, burn the copper conductor.

Since there is no approved procedure for in-vehicle testing of the flexible circuit, the instrument cluster must be removed from the vehicle for visual inspection. If no damage is evident, each circuit should be checked with an ohmmeter. If an open circuit or a short is detected, the flexible circuit must be replaced.

Gauge Indication Systems
The indication systems use magnetic gauges mounted in the instrument cluster. All the gauges are constructed with windings that form coils. Typically one coil is wound at a 90°C angle to the other two. The coils form a magnetic field which varies in direction according to the resistance of the sender, except the battery voltage gauge, that is connected between two of them. The battery voltage gauge varies in direction according to the battery voltage. A primary magnet, to which a shaft and pointer are attached, rotates to align to this primary field, resulting in pointer position. No instrument voltage regulator is used with this system. There is no adjustment, calibration or maintenance required for any gauges.

Instrument Cluster Gauge Amplifier/Check Gauge Module

NOTE:
- The fuel gauge and instrument cluster gauge amplifier must be replaced as a set. The fuel gauge and instrument cluster gauge amplifier are calibrated together.
- If the ignition key is left in the ON position during fueling, a slow to respond fuel gauge indication may result. The ignition key must be placed in the OFF position during or after refueling for accurate fuel gauge indication.

The instrument cluster gauge amplifier electrically averages the fuel sender readings so the gauge displays the actual fuel level and not the fluctuations due to fuel sloshing. The amplifier also supplies the signal to illuminate the CHECK GAGE indicator to indicate low fuel, high engine coolant temperature, or low engine oil pressure. The gauge amplifier is a small printed circuit board located in a pocket on the back of the instrument cluster. The electrical connections are made with a spring-type connector. There are no provisions for calibration or adjustment. The fuel gauge and the instrument cluster gauge amplifier must be replaced as a unit.

Fuel Sending Unit
The fuel sending unit is a variable resistor made up of a ceramic substrate. It is controlled by the action of a float arm. When the fuel level is low, resistance in the unit is low. When the fuel level is high, the resistance is high.

Water Temperature Indicator Sender Unit
When the engine temperature is low, the resistance of the water temperature indicator sender unit is high, thus restricting the flow of current through the gauge and moving the pointer only a short distance. As the temperature of the coolant increases, the resistance decreases, allowing more current to flow through the gauge and results in a corresponding movement of the pointer.

Oil Pressure Indicator Switch
The oil pressure switch is installed in the engine block and consists of a diaphragm and contact points. The contact points are closed with oil pressure causing the gauge to indicate NORMAL oil pressure. With no oil pressure, the contacts open and the gauge indicates low oil pressure.

Charge Indicator System
The battery voltage gauge measures the voltage potential at the battery.

Vehicle Speed Signal
The vehicle speed signal is generated by the rear anti-lock brake sensor and sent to the 4-wheel Anti-lock Brake System (4WABS) module. The 4WABS module sends the vehicle speed signal via circuit 679 (GY/BK) to all systems which require a vehicle speed signal input.

Speedometer
The electronic speedometer receives a speed signal from the 4WABS module.

Odometer
A million-mile tamper-resistant odometer is standard. Replacement speedometers have an odometer that can be reset to indicate correct vehicle mileage.

NOTE: Some state laws require that the odometer in any replacement speedometer must register the same as on the removed odometer. Replacement speedometers and odometer modules with the mileage preset are available through Ford electronic repair centers.

If the actual vehicle mileage cannot be determined, the repair centers are able to supply odometers set to "0" miles. An odometer mileage sticker is supplied with the replacement odometer. This sticker must display the estimated vehicle mileage and be affixed to the driver door jamb.

Trip Odometer
The trip odometer indicates how many miles the vehicle has been driven since the last reset.

Tachometer
The tachometer is a 6000 rpm tachometer. It has four terminals: one labeled B (12 to 1 4.5V), one labeled S (EDIS tach signal in), and two labeled G (cylinder selection grounds). The bottom ground (G) terminal is grounded. The top ground (G) terminal is grounded through a 4.32 kohm resistor in a 6-cylinder engine vehicle and is connected directly to ground for an 8-cylinder engine vehicle.

WARNING INDICATORS

Brake System
The red brake warning light (BRAKE) is used to indicate a low fluid level, brake malfunction or a parking brake that is not fully released. The brake fluid level switch is located in the brake fluid reservoir.

The yellow brake warning indicator is used to indicate a malfunction or deactivation of the anti-lock brake system (ABS). It illuminates when triggered by the ABS control module and stays illuminated as long as the malfunction remains in the system.

Charge System Warning Indicator
The charge system warning indicator illuminates when there is no Generator (GEN) output.

When the ignition switch contacts are closed, battery current flows through the charge indicator and the parallel resistor (390 ohm) to the voltage indicator, and the indicator illuminates.

When the generator builds up enough voltage to energize a circuit in the voltage regulator, the indicator goes out.

Check Engine Light
The CHECK ENGINE/malfunction indicator lamp (MIL) is illuminated when a Diagnostic Trouble Code (DTC) or malfunction is sensed in the closed loop by the Powertrain Control Module (PCM).

Air Bag
If an air bag system DTC or malfunction is detected, the air bag indicator is illuminated.

Safety Belt
The safety belt warning indicator is powered through the GEM/CTM module. When the ignition key is turned on, the indicator illuminates for four to eight seconds even if the safety belt is buckled.

Low Fuel
When the fuel level drops to a predetermined level, the CHECK GAGE indicator will illuminate.

Door Ajar
The DOOR AJAR indicator illuminates when any of the vehicle doors are open.

High Beam
The high beam indicator is illuminated when the high beams are on.

Overdrive (O/D) Off
The O/D OFF indicator illuminates when the transmission is locked out of O/D. This dual function indicator will also flash off and on if a transmission malfunction is detected.

Anti-Theft
Once triggered, the anti-theft system flashes the low beam headlamps, the parking lamps, the THEFT indicator and sounds the horns.

Speed Control
The Speed Control Indicator (SPEED CONT) lamp will illuminate when the speed control is engaged.

Fuel Reset
The FUEL RESET indicator is grounded through the inertia switch whenever the vehicle is subjected to a high force situation. The inertia fuel shutoff switch (IFS switch) cuts off the fuel pump motor. The FUEL RESET indicator illuminates when the IFS switch has been tripped.

Check Gage
The CHECK GAGE indicator will illuminate if any of the following occur:
- Engine oil pressure drops below approximately 42 kPa (6 psi).
- Fuel level drops below approximately 4 - 8 L (1 - 2 gal).
- Engine temperature exceeds approximately 121°C (250°F).

Rear Load Leveling (CHECK SUSP)
The CHECK SUSP indicator illuminates when there is a malfunction of the rear load leveling system or if the air suspension switch is in the OFF position.