Relay, Wiper, On And Off: Operation

WARNING: This page is about a different car, the 2017 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The wiper on and off relay within the Power Distribution Center (PDC) switches the input to the wiper high and low relay between the wiper motor park switch circuit and a fused ignition output (RUN/ACCESSORY) circuit. The Body Control Module (BCM) controls the electromagnetic coil of the relay using a High Side Driver (HSD). When the electromagnetic relay coil is energized, it draws and holds the normally open movable contact of the relay against the fixed relay contact. When the BCM de-energizes the electromagnetic relay coil, spring pressure returns the movable contact to the normally open position.

The open relay contacts direct fused ignition output (RUN/ACCESSORY) current from the PDC to the wiper high and low relay. The closed relay contacts directs either ground or fused battery current from the BCM to the wiper high and low relay, depending upon the status of the wiper motor park switch. The resistor within the relay is connected in parallel with the electromagnetic coil, and helps to dissipate voltage spikes that are produced when the coil is de-energized.

The hard wired inputs and outputs of the wiper on and off relay in the PDC and the BCM may be diagnosed using conventional diagnostic tools and procedures. Refer to the appropriate wiring information. However, conventional diagnostic methods will not prove conclusive in the diagnosis of the BCM or the electronic controls and communication between modules and other devices that provide some features of the BCM controlled wiper on and off relay. The most reliable, efficient and accurate means to diagnose the BCM or the electronic controls and communication related to BCM controlled wiper on and off relay operation requires the use of a diagnostic scan tool. Refer to the appropriate diagnostic information.