The Instrument Panel (I/P) Cluster Assembly receives power from the TRANS fuse 20, through CKT 1020 (PNK) to pin 15 of the IP Cluster connector. The GAUGES fuse 4 supplies power to pin 31 of the I/P Cluster connector.

Power coming in through pin 15 of the I/P Cluster supplies voltage to the Tachometer, Electric Speedometer, PRNDL Indicator, and the Check Gauges Lamp Driver. Pin 31 of the I/P Cluster carries power to the remaining components within the I/P Cluster Assembly:

Ground for the I/P Cluster Assembly goes through two pins. One is pin 23, the other is pin 11. Both run to splice S215 and onto ground G104 and G103 (Gas Only).

Magnetic fields of two coils moves the pointer of the fuel gauge. The coils are at right angles to each other. Battery voltage is applied to the E-coil (empty) and the circuit divides at the opposite end of the coil. One path continues to ground through the F-coil (full). Another path goes through CKT 30 (PPL) to ground on single tanks using the variable resistance of the level sensor in the fuel pump and sender (Gasoline) or the fuel gauge sender (Diesel).

When the tank is low, the resistance of the level sensor is low. A large current flow passes through the E-coil and the pointer moves toward E on the fuel gauge. When the tank is full, the level sensor resistance is high, and less current passes through the E-coil, and the pointer moves toward F on the scale. With two coils operating the pointer, the fuel gauge is not affected by changes in the system's battery voltage.

The oil pressure gauge displays the engine oil pressure. Current flow through two coils moves the pointer of the gauge and is similar in operation to the fuel gauge. The oil pressure sender senses engine oil pressure sending resistance through CKT 31 (TAN) to pin 7 of the I/P Cluster.

The oil sender has a low resistance (approximately 0 ohms) when the oil pressure is low (0 psi), and a high resistance (approximately 90 ohms) when the oil pressure is high (80 psi).

The temperature gauge displays the engine coolant temperature. Current flow through two coils moves the pointer of the gauge and is similar in operation to the fuel gauge. The engine coolant temperature sender sends resistance through CKT 35 (DK GRN) to pin 9 of the I/P Cluster.

The engine coolant temperature sender has low resistance at higher temperatures. The sender has a resistance of approximately 49.5 ohms at 123°C (260°F). The sender resistance increases at lower temperatures and is approximately 1305 ohms at 47°C (100°F). This causes the current through the sensor to increase as the coolant temperature increases and the temperature gauge pointer then moves toward the hot end of the gauge.

The voltmeter measures the electrical system's voltage when the ignition switch is in the RUN or START position. The voltmeter measures battery voltage when supplied to the instrument cluster.

With the engine running, the normal reading is between 12-16 volts. The indication may decrease to 9.5 volts in cold weather with the engine stopped and ignition in the RUN position.

The Speedometer, grounded through the I/P Cluster ground circuit, receives its speed signal from either the VCM (Gas) or PCM (Diesel) through CKT 389 (DK GRN), which connects to the I/P Cluster at pin 10.

The tachometer, also utilizing the I/P Clusters ground, displays the engine speed in revolutions per minute (RPM). Voltage pulses are taken from the ignition control (Gasoline) or the generator (Diesel) through CKT 121 (WHT) and sent to the tachometer through pin 8 of the I/P Cluster. Solid state circuits convert the pulse frequency in order to move the pointer of the tachometer.

The PRNDL indicator shows the gear selection for an automatic transmission (AT). Voltage for the PRNDL indicator comes through pin 15 of the I/P Cluster. The following four circuits pass coded input from Transmission Range (TR) Switch (part of the park/neutral position (PNP) switch) to the solid state within the PRNDL indicator.

The illuminated gear selection depends on the combination of circuits grounded. Refer to PRNDL Logic Input Test, 1999 C/K Service Manual for indicator combinations.

The check gauges lamp illuminates when the engine oil pressure is low or the engine coolant temperature is high.

The instrument cluster's check gauges lamp driver, solid state logic, monitors the input signals to the oil pressure gauge and the temperature gauge.

When the ignition switch is turned to the RUN or the START position, the check gauges lamp driver grounds the check gauges lamp when either of the input signals exceed the set point. this causes the lamp to illuminate. The lamp is normally illuminated when the ignition switch is turned to the RUN position. The lamp turns off when the engine is started and the oil pressure increases above the set point. All connections of the check gauges lamp driver are within the I/P Cluster Assembly.

Power for the Water In Fuel Lamp is supplied by pin 22 of the I/P Cluster. Ground for this lamp is provided by the Water In Fuel Sensor, located on the Fuel Filter housing. When water is detected by the sensor, solid state internals within the sensor provides ground through CKT 508 (YEL/BLK) and pin 18 of the I/P Cluster Assembly.