Bronco L6-300 4.9L VIN Y 1-bbl (1983)
Temperature Gauge: Testing and Inspection
Dash Gauge Test
Gauge failures are often caused by defective wiring or grounds. The first step in locating trouble should be a thorough inspection of all wiring,
terminals and printed circuits. If wiring is secured by clamps, check to see whether the insulation has been severed, thereby grounding the wire. In the
case of a fuel gauge installation, rust may cause failure by corrosion at the ground connection of the tank unit.
The Constant Voltage Regulator (CVR) type indicator is a bimetal-resistance type system consisting of an Instrument Voltage Regulator (IVR), an
indicator gauge, and a variable resistance sending unit. Current to the system is applied to the gauge terminals by the IVR, which maintains an
average-pulsating value of 5 volts.
The indicator gauge consists of a pointer which is attached to a wire-wound bimetal strip. Current passing through the coil heats the bimetal strip,
causing the pointer to move. As more current passes through the coil, heat increases, moving the pointer farther.
The circuit is completed through a sending unit which contains a variable resistor. When resistance is high, less current is allowed to pass through the
gauge, and the pointer moves very little. As resistance decreases due to changing conditions in system being monitored, more current passes through
gauge coil, causing pointer to move farther. Do not apply battery voltage to system or ground output terminals of IVR, as damage to system components
or wiring circuits may result.
DASH GAUGE TEST
1.
Disconnect battery ground cable and remove gauge from vehicle.
2.
Connect ohmmeter between gauge terminals and read coil winding resistance.
3.
An upward movement of ohmmeter needle from 10 ohms to 14 ohms is normal, as test current of ohmmeter causes a temperature rise in gauge coil
windings.
4.
If ohmmeter reads below 10 ohms or above 14 ohms, gauge is defective.
