Symptoms of a Bad or Failing Intermittent Wiper Relay

Whether you're driving in a torrential downpour or simply need to clear those bugs off the windshield, having the ability to slow down or speed up your windshield wipers comes in quite handy. This operation is completed thanks to the intermittent wiper relay; an electrical switch that sends a predetermined setting to the wiper module to power the wiper motor. When all of the components involved in the windshield wiper blades work correctly, the system is very convenient. However, when one part malfunctions, it can cause potential safety concerns. One of the most common parts to fail is the intermittent wiper relay switch.

The electronic relays that are installed in today's cars, trucks and SUV's have to operate in very hot and grueling conditions or are subject to constant abuse. The wiper relay is unique in that it's found inside the wiper control handle which often has selector switches giving drivers multiple settings for their windshields. Over a period of time, this relay can be damaged – which will impact the operation of the windshield wiper system and in some cases, render it useless.

When the intermittent wiper relay begins to fail or is wearing out, it will display a few warning signs to the driver. In order to reduce the potential of damage to other mechanical components, it's important to be alert to these symptoms and take proactive measures to have the intermittent wiper relay replaced if needed by a professional mechanic. Listed below are a few of these warning signs.

1. The windshield wiper blades have one speed

One of the quickest indicators that a problem exists with the intermittent wiper relay is when the wipers are not intermittent and only work at one speed. The relay switch sends an electrical signal to the module that controls the operation of the wiper motor and gears inside. When the relay is faulty, the windshield wipers will only work at the same speed that the last relay signal was sent. In layman's terms, if you had your windshield wipers on the slow speed the last time they were active, and you turn them on again under a different setting, the relay switch should send that updated information to the module. If you make a change in the settings and the wipers don't react, it's most likely due to a malfunction in the intermittent wiper relay.

This can lead to a potentially unsafe driving situation as sometimes we encounter weather conditions that require the use of the intermittent switch. If you notice this problem on your windshield wipers, please contact a certified mechanic as soon as possible.

2. The windshield wiper blades don't work

Since the intermittent wiper relay is responsible for sending signals to the module, it's also possible that it could send an incorrect signal when it is malfunctioning. Most of the time, this signal will be to the motor to cease operation of the wiper blades. This is very rare, but is often attributed to a problem in the intermittent wiper switch or controls.

3. Wiper blades operate at speeds different than you selected

Similar to the issue above, if you notice that your wiper blades are operating at a different speed or intermittent setting than you selected, it's a good indication that the relay is damaged and needs to be replaced. This is also a symptom that you don't want to avoid as it may cause the wiper blade motor to overheat and break prematurely.

4. Humming noise when the wipers are on

In some instances, you may notice that there is a strange humming noise when trying to operate the wipers on the car. This is usually caused by the wiper motor not getting the power that it needs due to a bad relay. In most cases, a professional mechanic will replace the intermittent wiper relay and the controls at the same time to ensure all of the supporting connections work smoothly together.

Having a fully functional intermittent wiper relay is more than a convenience. For many of us that are subject to driving in evolving and changing weather conditions; it's imperative for safe visibility. If you notice any of the above warning signs, make sure to contact a local ASE certified mechanic from YourMechanic.com to replace your wiper relay.


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