Compass 2WD L4-2.4L (2008)
Check Valve: Description and Operation
Operation
OPERATION
The rear check valve provides more than one function in this application. It prevents washer fluid from draining out of the rear washer supply hoses back
to the washer reservoir. This drain-back would result in a lengthy delay from when the rear washer switch is actuated until washer fluid was dispensed
through the rear washer nozzle, because the washer pump would have to refill the rear washer plumbing from the reservoir to the nozzle. Such a
drain-back condition could also result in water, dirt, or other outside contaminants being siphoned into the washer system through the washer nozzle
orifice. This water could subsequently freeze and plug the nozzle, while other contaminants could interfere with proper nozzle operation and cause
improper nozzle spray patterns. In addition, the rear check valve prevents washer fluid from siphoning out through the rear washer nozzle after the rear
washer system is turned OFF.
When the washer pump pressurizes and pumps washer fluid from the reservoir through the rear washer plumbing (5), the fluid pressure unseats a
diaphragm (3) from over a sump well within the valve by overriding the pressure applied to it by a piston (2) and coiled spring (1). With the diaphragm
unseated, washer fluid is allowed to flow toward the rear washer nozzle (4). When the washer pump stops operating, the spring pressure on the piston
seats the diaphragm over the sump well in the valve and fluid flow in either direction within the rear washer plumbing is prevented.
