Circuit Operation - Gauges Cluster

Only those indicators and gages that are not described in connection with other circuits are explained in this circuit operation. See the circuit referred to for its complete operation.

Tachometer
The Tachometer displays engine speed in rpm. Voltage pulses are taken from the Electronic Ignition (EI) System and sent to the Tachometer. It responds to the frequency of the voltage pulses which increase with engine speed. Solid state circuits process these pulses into a signal that drives the pointer of the meter.

Fuel Gage
The pointer of the Fuel Gage 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 Gage Sender.

When the tank is low, the resistance of the sender is low (0 ohms). 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 (90 ohms). More current flows through the F coil, moving the pointer toward F on the scale.

With two coils operating the pointer, the gage is not affected by changes in the voltage of the system.

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 Fuel Pump Switch coil 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 0 to 550 kPa (80 psi).

Engine Coolant Temperature Gage
The Engine Coolant Temperature Gage is operated by two coils. Battery voltage is applied to both coils. One is grounded directly and the other is grounded through the Coolant Temperature Sender/Sensor. This has 63 ohms resistance at 125°C (260°F) (hot coolant) and its resistance increases at lower temperate. Resistance is approximately 1365 ohms at 40°C (1000°F). This causes the current through the sender and one coil to increase as the engine coolant temperature increases. This moves the pointer.

Shift Indicator (Manual Transaxle Only)
In the LA VIN 4 and V6 VIN T with Manual Transaxle, a bulb lights when the vehicle should be shifted to the next higher gear for better fuel economy. Battery voltage is applied to one side of the bulb. The other side of the bulb is switched to ground by the Engine Control Module (ECM), which uses engine data such as rpm, vehicle speed, and intake vacuum to compute an efficient shift point.

Speedometer
The Speedometer pointer is moved by the magnetic fields 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 ECM. The ECM processes 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 (V6 VIN T ONLY)
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.

Daytime Running Lights On Indicator (Daytime Running Lights Only)
The Turn Lights On Indicator receives battery voltage with the Ignition Switch in RUN and ground through the many Tail Lights with the Headlight Switch in OFF. This forces the indicator ON with the Ignition Switch in RUN and the Headlight Switch OFF. In daylight this indicator is barely visible, but in low light the indicator becomes visible. When the Headlight Switch is in PARK or HEAD, battery voltage is applied to the ground side of the indicator. With battery voltage on both sides of the indicator, it goes out.

Gate Ajar Indicator
With the Ignition Switch in RUN, BULB TEST or START, voltage is applied to the Gate Ajar Indicator. The Indicator receives a path to ground when the Gate Ajar Switch closed. The switch closes with the gate unlatched.

Check Gages Indicator
The CHECK GAGES Indicator is controlled by a solid state indicator control unit. Inputs are received from the Coolant Temperature Sender/Sensor, Oil Pressure Sender and Fuel Gage Sender. When any of these sender resistances changes to the point where its gage indicates a warning condition, the Check Gages Buffer turns on the Indicator.