TD5 Defender
19
FUEL SYSTEM
10
DESCRIPTION AND OPERATION
WATER SENSOR
The water sensor has a three pin electrical connector. When the sensor detects water in the fuel filter it illuminates
a warning lamp in the instrument pack.
The water sensor attachment thread has a slot machined down one side. The filter can be purged of water by
partially unscrewing the sensor which aligns the slot in the threads with a corresponding hole in the sensor. When
aligned, water and fuel can flow down the slot and flows from a small cast tube on the side of the sensor.
Re-tightening the sensor mis-aligns the slot and stops the flow of fuel.
The sensor operates by measuring the resistance between its two electrodes, which are submerged in fuel, and
activated by the presence of water. When the ignition switch is moved to position ’II’, the warning lamp will
illuminate for approximately 2 seconds to check warning lamp functionality.
When the filter is full with fuel and no water is present, the resistance of the Diesel fuel will show a reading of 15
mA maximum on the feed wire to the instrument pack. When sufficient water surrounds both electrodes, the
resistance of the water will show a reading of 130 mA maximum. This will supply sufficient voltage to the
instrument pack to illuminate the warning lamp, and alert the driver to the presence of water in the fuel system.