Washer Fluid Level Indicator: Description and Operation

There are two types of low washer fluid indicating systems. They are the mechanical type and electrically controlled type. The mechanical type consists of a float and rod assembly, sending unit and a fiber optic. The electrically controlled type consists of a float, magnet, contact points and a resistor.
On the mechanical type, the upper end of the rod extends into the sending unit and has colored red and green portions. When the windshield wipers are activated, a lamp bulb in the sending unit lights either the red or green sections of the rod. The colored light is then picked up by the fiber optic and is transmitted through it to the telltale lens. The lens will show red or green depending upon washer fluid level.
The electrically controlled indicator is activated when the windshield wipers are engaged. A slight amount of current flows from the wiper motor to the washer bottle float unit. This current will either pass through the contact points or the resistor which is in parallel with the points. When the washer fluid level is high, the magnet holds the contact points open. The current will now flow through the resistor where it is reduced so the indicator will not light. When the washer fluid level is low, the float drops and the magnet will separate from the cap assembly allowing the current to pass through the contact points and activate the indicator light.