Component Tests and General Diagnostics
The Rotunda Instrument Gauge System Tester Model 021-00055 or equivalent is used to diagnose problems with the instrument cluster magnetic gauges. Testing of the magnetic gauges can be accomplished by:
1. Disconnect connector from the appropriate sender and hook onto the matching terminals on the tester.
2. Turn the vehicle ignition switch lock cylinder (11582) to ON position.
a. Disconnect connector from sender. Turn the ignition switch lock cylinder to ON. For coolant temperature connect a 9.7-ohm resistor between the connector and ground. For oil pressure short the connector directly to engine ground. The centerline of the pointer should fall within the band around the "H" mark for coolant temperature and slightly above mid-scale for oil pressure.
Fuel Gauge
With the sending unit float arm in the empty stop position resistance should be 15 ohms (below E). With the sending unit float arm in the full-stop position resistance should be 160 ohms (above F). The fuel gauge (9280) should read empty at 22.5 ohms and full at 145 ohms.
Fuel Tank Sending Unit
With ohmmeter positive lead on the signal wire lead and the negative lead on ground check the resistance values of the fuel sending unit at various positions of the float arm. An open circuit will indicate infinity on the ohmmeter and a short will indicate zero ohms.
Coolant Temperature Gauge
Connect a 74-ohm resistor between the gauge lead and ground. The center line of the pointer should fall within the band around the "C" mark.
^ If the engine coolant temperature gauge (10883) tests within calibration replace engine coolant temperature sensor (ECT sensor) (12A648).
^ If the engine coolant temperature gauge still tests out of calibration replace the gauge.
Coolant Temperature Indicator Sender Unit
If the engine coolant temperature gauge is still not indicating properly check the engine coolant level to make certain that coolant level is still at full point. Also verify that water thermostat (8575) is operating and that fan belt tension is within specification.
Oil Pressure Gauge/Oil Pressure Sender
With connector attached to the oil pressure sensor (9278) and ignition switch lock cylinder on the center line of the pointer should fall on or below the "L" mark.
^ If the oil pressure gauge (9273) tests within calibration replace oil pressure sensor.
^ If the oil pressure gauge still tests out of calibration replace the gauge.
Charge Indicator Lamp
The integral alternator regulator (IAR) has a circuit in the voltage regulator that will indicate a high battery (10655) voltage condition. With the IAR system two conditions can cause the charge indicator lamp to come on during vehicle operation:
1. No generator (GEN) (10346) output - damaged generator voltage regulator or wiring.
2. Overvoltage correlation - shorted generator rotor regulator or wiring.
If the system is working normally the following conditions will be present:
^ With ignition switch lock cylinder in OFF position charge indicator (battery symbol) lamp is off.
^ With ignition switch lock cylinder in RUN (engine not running) charge indicator (battery symbol) lamp is on.
^ With ignition switch lock cylinder in RUN (engine running) charge indicator (battery symbol) lamp is off. Except as noted above.
If the charge indicator lamp does not come on with the ignition switch lock cylinder in the RUN position (engine not running) check the "I" circuit (ignition switch lock cylinder to regulator "I" terminal) for an open circuit or burned out charge indicator lamp. Replace the lamp if necessary.
3. If the charge indicator lamp does not come on disconnect the wiring connector from the voltage regulator.
4. Connect a jumper wire from the wiring connector "I" terminal to the battery negative post cable clamp.
5. Turn the speedometer to RUN (engine not running). If the indicator lamp does not light check the indicator bulb for continuity and replace the bulb if it is burned out. If the bulb is still good perform the voltage regulator "I" circuit tests.
Odometer Accuracy Test
To test the odometer (17A265) accuracy drive the vehicle over a measured distance of at least 10 consecutive miles (or 16 kilometers). Check measured distance against odometer measured distance. Acceptable odometer measured distance is 15.5-16.7 km (9.6-10.4 miles).