Instrument Panel, Gauges and Warning Indicators: Description and Operation

The operation of an individual Gage or Indicator is described along with its circuit.

BRAKE WARNING LAMP

Battery voltage is applied to the Brake Indicator when the Igntion Switch is in RUN or START. there are three methods to provide a ground to light the Brake Indicator.

The Park Brake Switch provides a ground when the Park Brake is applied. the Brake Indicator lights to alert the driver.

The Brake Pressure Switch closes to illuminate the Brake Indicator when there is low brake fluid pressure in one of the two hydraulic brake systems. This could be caused by a leak in one of the brake lines.

The Electronic Rear Wheel Brake Control Module provides a ground for the Brake Indicator whenever the Ignition Switch is turned to RUN for three seconds for a bulb check. When the Electronic Rear Wheel Brake Control Module detects a problem within its system it will provide a ground for the Brake Indicator.

FUEL GAGE

The pointer of the Fuel Gage is moved by the magnetic fields of two coils. The coils are not at right angles to each other. Battery voltage is applied to the E-coil and the circuit divides at the opposite end of the coil. One path continues to ground through the F-coil. Another goes to ground through the variable resistor of the Fuel Gage Sender.

When the tank is low, the resistance of the Sender is low. A large flow of current passes through the E-coil and the Fuel Gage Sender resistor. this moves the pointer toward E on the scale. When the tank is full, the Sender resistance is high. More current now flows through the F-coil, moving the pointer toward F on the scale.

With the two coils operating the pointer, the Gage is not affected by changes in the system's battery voltage.

OIL PRESSURE GAGE

The engine oil pressure is displayed by the Oil Pressure Gage. The pointer of the Gage is moved by two coils, and its operation is similar to that of the Fuel Gage.

The Oil Pressure Sender is connected to the junction of the two coils. It has low resistance when the oil pressure is low and 90 ohms resistance when. The oil pressure is high. This changing resistance changes the current flow through the coils. The magnetic fields of the coils move the pointer from low to high.

TEMPERATURE GAGE

The Temperature Gage is also operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Temperature Sender. This has 55 ohms resistance at 128~C (260~F) (hot coolant) and its resistance becomes greater at low temperatures. It is approximately 1400 ohms at 38~C (100~F). This causes the current through the Sender and one coil to increase as the coolant temperature increases. This moves the pointer.

LOW COOLANT LEVEL WARNING (DIESEL)

The Low Coolant Level Warning Module receives voltage from line (39) when the Ignition Switch is in RUN or START.

The resistance across the Low Coolant Level Sensor, which is placed in the radiator, increases when the coolant level goes low, causing the Low Coolant Level Module to produce a current flow through the indicator bulb. Illumination of the Low Coolant Level Warning bulb alerts the driver to this condition.

VOLTMETER

The Voltmeter shows the battery voltage. The Voltmeter is connected across the 39 (PNK/BLK) wire and the 150 (BLK) circuits of the cluster.

CLUSTER ILLUMINATION

The Cluster Illumination Lamps are provided voltage by the Light Switch through the INST LPS Fuse and the GRA (8) wire. Ground for the lamps is provided through the BLK (150) wire.