Base Instrument Cluster - Manual Update: Overview
FILE IN SECTION: 8 - Chassis/Body ElectricalBULLETIN NO.: 53-81-04
DATE: January, 1995
SUBJECT:
Section 8A - Revised Cell 80: Instrument Cluster - Base Cluster (RPO U23)
MODEL:
1994 Oldsmobile Achieva
This bulletin revises Section 8A, Cell 80: Instrument Cluster - Base Cluster, U23 of the Service Manual.
CIRCUIT OPERATION
Only those indicators and gauges that are not described in connection with other circuits are explained in this circuit operation. For the complete operation of other indictors and gauges, see the circuit referenced on the schematic.
FUEL GAUGE
The pointer of the Fuel Gauge is moved by the magnetic field of two coils. The coils are at right angles to each other. Battery voltage is applied to the E coil and the circuit divides at the opposite end of this coil. One path continues to ground through the F coil. The other path grounds through the variable resistor of the Fuel Gauge Sender.
When the tank is low, the resistance of the sender is low (0 ohms). A large 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 (90 ohms). More current flows through the F coil, moving the pointer toward "F" on the scale.
With two coils operating the pointer, the gauge is not affected by changes in the voltage of the system.
SPEEDOMETER
The Speedometer pointer is moved by the magnetic field of two coils. These coils are driven by a solid state unit.
The Vehicle Speed Sensor located in the transaxle generates an AC voltage that is sent to the Engine Control Module (ECM). The ECM processors this voltage into a square wave. The pulses generated are sent to the Speedometer at 4000 pulses per mile.
ODOMETERS
Both the Trip Odometer and the Total Odometer are mechanical displays. Each is driven by an electric motor that is fed from the solid state circuit board. These stepper motors turn in response to the number of pulses received from the ECM.
LOW COOLANT INDICATOR
The LOW COOLANT Indicator comes on to warn the driver when a low level of coolant exists in the Surge Tank. Voltage is supplied to the LOW COOLANT Indicator with the Ignition Switch in "RUN," "BULB TEST" or "START" When a low level of coolant exists, the Surge Tank Low Coolant Switch closes, providing ground for the LOW COOLANT Indicator.
CHECK OIL INDICATOR
The CHECK OIL Indicator lights to warn the driver that the engine oil level is low. When the Ignition Switch is first moved to "RUN," the oil level indicator lights for about 1 and 1/2 seconds as a bulb check. The oil level detection circuit has two internal timers. The first timer records the amount of time that the ignition has been off. The second timer records the amount of time that the ignition had been in "ON" before the ignition was shut off. The instrument panel cluster uses this information to determine if the engine has been sitting long enough for the engine oil to have returned to the engine oil pan. The cluster's oil level monitoring circuits will check the oil level switch if one of the following two conditions are true:
1. The ignition has been off for more than 30 minutes.
2. The ignition has been off for at least 3 minutes after the ignition has been on for at least 12 minutes.
If the oil level is low (Oil Level Switch open), the CHECK OIL Indicator will be turned on for the remainder of the ignition cycle. The oil level is monitored by the cluster only when the ignition is first moved to "RUN." It does not continuously monitor the engine oil level.