Rick's Free Auto Repair Advice

Intermittent Wipers Quick Fix

Fix for Intermittent Wipers

I learned this one from a blog reader:

I trouble shot my wife’s 1999 Plymouth Voyager for an intermittent wipers malfunction, to no success, I had replaced the multifunction switch ($175) based on incorrect resistance values posted in the Haynes Repair Manual. (Haynes provided a correction via mail).

The actual problem I found was that the intermittent wiper mode is dependent upon the wipers being properly parked. The parking action is through regenerative electrical braking of the wiper motor, the voltage of which is actually returned to ground through one pole of the wiper-on-relay. I caught on after hours of troubleshooting when I noticed the intermittent wipers did not work if the wiper blades were not parked exactly in the correct spot on the windshield.

Because of the low power generated by the regenerative braking, the NC pole (87A) of the wiper on relay does not benefit from the arcing that cleans the relay contacts under normal high current draw. It will become corroded and exhibit high resistance. An easy fix is to swap the wiper on and wiper high/low relays, or install a new wiper on relay. Wiper relays are located in the IPC integrated Power Module.

wiper relay, power distribution layout, relay layout

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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