Gauges & Indicators

Alternator Indicator

1) If light is on when ignition is off, check for shorted alternator positive diode. If light is off with ignition on and engine off, check for burned out indicator bulb, open light circuit or open in alternator field.

2) If light comes on with engine running at greater than idle RPM, check alternator output. Check for loose alternator belt. Check for shorted alternator negative diode. See BENCH TESTS under ALTERNATORS and REGULATORS.

Brake System Warning Indicator

1) If brake system warning indicator stays off, check for blown fuse. If brake indicator remains on with ignition switch in "RUN" position and parking brake off, a defective parking brake switch or a leak in one of the brake systems is indicated.

2) Verify leakage by removing electrical connector from brake pressure switch. If indicator goes out, brake pressure switch was closed (low pressure in one system). Repair as necessary. If indicator remains on, check for short in parking brake switch, ignition switch or wiring.

3) If brake indicator comes on when ignition switch is in "START" position, but not when parking brake is on, measure voltage at Tan/White parking brake switch wire with ignition switch in "RUN" position and parking brake applied.

4) If battery voltage is at Tan/White wire, install a new parking brake switch. If zero voltage is at Tan/White wire, check wire for open between switch and bulkhead connector (front of dash, left side).

5) If brake indicator comes on with parking brake on, but not when ignition switch is in "START" position, check for voltage at ignition switch "START" terminal. If battery voltage is not found, install new ignition switch.

6) If no voltage is found, check Tan/White wire for open between ignition switch and bulkhead connector. If brake indicator does not come on with low brake accumulator pressure, check for battery voltage at brake accumulator pressure switch terminal (Tan/White wire). If voltage is not found, install new switch.

Coolant Indicator

1) If "HOT" indicator fails to light when cranking engine, check for burned out bulb, open light circuit, or defective ignition switch.

2) If indicator light remains on with engine running, check for excessive coolant temperature, defective sending unit or ground in wire between bulb and sending unit.

Fuel Gauge (Accuracy Test)

1) Use Fuel Gauge Tester (J-33431). Disconnect fuel gauge sender connector. Turn ignition switch to "RUN" position. Clip tester leads to Black wire and Pink or Purple wire of harness connector.

2) Set resistance dials of tester to zero ohms (empty) and to 90 ohms (full). If gauge responds correctly, replace fuel gauge sender. If not, replace fuel gauge.

Fuel Gauge Always Reads Empty

1) Disconnect fuel gauge sender Pink or Purple wire. Turn ignition switch to "RUN" position. Gauge should indicate full.

2) If gauge does indicate full, replace fuel gauge sender. If gauge does not indicate full, check Pink or Purple wire for a short to ground. If Pink or Purple wire is okay, replace fuel gauge.

Fuel Gauge Always Reads Full

1) Disconnect fuel gauge sender Pink or Purple wire. Connect a jumper wire between harness half and ground. Turn ignition switch to "RUN" position. Gauge should indicate empty.

2) If gauge does indicate empty, check Black wire between fuel gauge sender and ground for an open. If wire is okay, check fuel gauge sender using ohmmeter.

3) If sending unit is good and gauge still indicates full, check Pink or Purple wire for an open. If Pink or Purple wire is okay, replace fuel gauge.

Oil Indicator

1) If light does not come on with ignition on and engine not running, check for burned out bulb, light circuit open, or defective sending unit.

2) If light remains on when engine is running, check for grounded wire between bulb and sending unit, defective sending unit, or low oil pressure.

Tachometer

1) With engine running, measure voltage at tachometer input connector White wire. Voltmeter should indicate 1-10 volts and varying with engine RPM. If voltmeter does not indicate correctly, check White wire for an open.

2) If White wire is okay, Computer Controlled Coil Ignition (C(3)I) system is at fault. If voltage readings are correct, replace instrument cluster.

Tailgate Ajar Light (No Light)

With ignition switch in "RUN" position, disconnect wire from tailgate switch and touch wire to known good ground. Light should glow. If light fails to glow, bulb is burnt out or circuit (Black/Orange and Orange) is open.

Tailgate Ajar Light (Stays On)

Check circuit for short to ground after bulb. If short to ground is not present, replace switch.

Voltmeter

1) If voltmeter reading on vehicle is inconsistent with battery voltage reading remove instrument panel. Connect a known accurate voltmeter. Turn ignition switch to "RUN" position. Test voltmeter should show true voltage.

2) If test voltmeter shows accurate voltage, replace vehicle voltmeter. If test voltmeter does not show accurate battery voltage, check circuit for an open.