Instrument Cluster / Carrier: Description and Operation

Coolant Temperature and Fuel Gauges

The coolant temperature gauge and the fuel gauge are each operated by two intersecting coils wound around a permanent magnet rotor. When voltage from fuse 1 is applied to the coils, a magnetic field is gene rated. 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 gauge needle moves according to the changing magnetic field.

The coolant temperature sending unit's resistance varies from approximately 142 ohms at low engine temperature to approximately 32 ohms at high temperature (radiator fan running).

The fuel gauge sending unit's resistance varies from approximately 5 ohms at full to approximately 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.

WARNING!

Do not smoke while working on the fuel system Keep open flame away from the work area.


Tachometer

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 250 pulses per minute from the ICM, the tachometer displays 100 rpm.


Speedometer and Odometer

The odometer driving circuit and the speedometer driving circuit receive pulses from the vehicle speed sensor (VSS) and, in turn, drive the odometer stepper motor and speedometer respectively.