Gauges

The engine coolant temperature gauge and the fuel gauge are each operated by two intersecting coils wound around a permanent magnet rotor. When voltage is applied through fuse 1 to the coils, a magnetic field is generated. This causes the rotor to rotate and the gauge needle to move. The magnetic field is controlled by the sender. As the resistance in the sender varies, current through the gauge coils changes. The needle then moves according to the changing magnetic field.

The engine coolant temperature (ECT) sender's resistance varies from about 142 ohms at low engine temperature, to about 13 ohms at high temperature.

The fuel gauge sender's resistance varies from about 5 ohms at full, to about 110 ohms at empty. Damping oil surrounding the fuel gauge keeps the gauge needle at the last level indicated before the ignition was shut off.

With the engine running, the tachometer senses ignition pulses from the distributor through the ignition control module (ICM). The solid-state tachometer displays these pulses as engine speed. For each 200 pulses per minute from the module, the tachometer displays 100 rpm.

The odometer drive circuit and the speedometer drive circuit receive pulses from the speed sensor amplifier and, in turn, drive the odometer stepper motor and speedometer respectively.