3 Symptoms of a Bad Wiper Relay (and Replacement Cost in 2025)

Have your windshield wipers been acting up lately? Though several different things can cause malfunctioning wipers, one common culprit is a failing wiper relay.

This often-overlooked component plays a major role in your vehicle’s wiper system, and when it starts to fail, it’ll show specific warning signs. Let’s look at the three main symptoms of a bad wiper relay, how to confirm the problem, and how much it’s going to cost to fix.

What Is a Wiper Relay?

The term “wiper relay” refers to one or more relays located within the windshield wiper control circuit of vehicles featuring intermittent wipers. Intermittent wipers, which are now standard on virtually all vehicles, foreign and domestic, allow drivers to vary the speed and frequency of wiper operation.

Some vehicles are manufactured with a single inline relay within the windshield wiper circuit, while others utilize multiple relays, governing various speeds/frequencies of operation. Additionally, many vehicles also feature a wiper “park” relay, which facilitates the return of both wiper arms to their home position after use.

How It Works

A vehicle’s intermittent windshield wiper relay works by delivering power to the wiper motors, at a set interval of time, thereby allowing wipers to operate in a manner that is sufficient for the amount of rainfall experienced. Essentially, this relay acts as an agent of power delivery, on behalf of commands sent via a designated controller.

In most applications, the module or controller mentioned above receives input signals from a vehicle’s multi-function switch (a lever on the steering column that has multiple control switches), as wiper speed selections are made by the driver.

As a result, an output is fielded by the module in question, that is delivered to the coil side of the intermittent wiper relay. Contacts are then bridged within the relay itself, allowing further power distribution to the wiper motor.

Location

In most cases, all relays relating to windshield wiper function are found within the underhood junction/fuse box of the vehicle. This junction box is typically mounted within one specific side of the engine compartment or the other, depending upon the make and model of the vehicle.

Usually, a locator diagram will be affixed to the underside of the lid of a vehicle’s junction box, detailing which relay relates to a particular circuit.

It’s worth mentioning that not all vehicles are equipped with wiper relays. A growing number of late model vehicles modulate wiper operation via the body control module, meaning that intermittent operation and speed control are not sustained via traditional relays.

Bad Wiper Relay Symptoms

When a windshield wiper relay starts to fail, it typically shows specific warning signs. Recognizing these symptoms can help you diagnose the problem quickly and avoid unnecessary repairs. Here are the most common signs to watch for:

#1 – Erratic Wiper Function

You may notice that your vehicle’s windshield wiper function seems erratic at times, whenever an intermittent wiper relay is at the early stages of failure.

Under these circumstances, a wiper motor might not energize as expected, only to engage unexpectedly moments later. This is generally caused by continuity issues within the affected relay.

If your wipers continue running or won’t turn off completely, this might indicate a different problem.

#2 – Lack of Wiper Function at Certain Speeds

Another classic sign of intermittent windshield wiper relay failure is a lack of delay in wiper operation or a lack of wiper operation at certain speeds. This is typical of systems that use a specified relay for intermittent function, that is not utilized at higher speeds. In this case, the relay in question is failing to latch as it otherwise should.

#3 – Inoperable Wipers

In some cases, a failed intermittent wiper relay can lead to full or very limited wiper operability. This occurs when the affected relay fails to latch, preventing power from being distributed to the vehicle’s wiper motor.

Replacement Cost (Professional and DIY)

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The cost associated with windshield wiper relay replacement is typically minimal, with a replacement relay itself being able to be sourced for approximately $10 to $20, in most cases.

If this relay is to be replaced at a dealership or other reputable service center, you can expect to pay an additional ½ hour’s labor rate, or approximately $50, bringing repair costs to a total of $70.

If you have basic mechanical skills, you can likely replace the windshield wiper relay yourself. This DIY approach will save you money on repair costs.

Diagnostic Steps

Before replacing a windshield wiper relay, you’ll want to confirm that the relay itself is the source of your wiper system issues. Following these diagnostic steps can save both time and money by preventing unnecessary parts replacement.

Step 1: Check the Fuses

Begin by checking your vehicle’s wiper system fuses, as these are typically the most common point of failure within any electrical circuit. These fuses can be located using the fuse panel diagram specific to your vehicle, typically found within the owner’s manual or on the interior of the fuse box cover itself.

Step 2: Test the Wiper Switch

Verify that your windshield wiper switch is functioning correctly. This can be accomplished by testing wiper function across all available speed settings. If wipers work at certain speeds but not others, this points more definitively toward a relay issue rather than a switch malfunction.

Step 3: Use a Multimeter

For those with access to a multimeter, testing the relay itself can provide concrete evidence of failure. With the relay removed, use the multimeter to check for continuity between specific pins while applying 12V to the relay’s control circuit.

If working correctly, a relay will show continuity when energized and no continuity when de-energized.

Step 4: Listen for the Click

Listen for an audible “click” when the relay is energized, either by operating the wiper switch or by manually applying power to the relay’s control circuit. The absence of this clicking sound often indicates relay failure, though this should not be used as the sole diagnostic criteria.

Step 5: Check the Park Position

In cases where wipers fail to return to their “park” position, the issue might involve the park relay rather than the primary wiper relay. Testing both components independently can help isolate the true source of the problem.

Step 6: Inspect the Wiring

Lastly, inspect all relevant wiring connections for signs of corrosion, damage, or loose fitment. Wiring issues can sometimes be similar to the symptoms of relay failure and should be ruled out before proceeding with relay replacement.

How to Replace a Wiper Relay

corroded headlight relay — corroded relay

Follow these steps to replace your faulty windshield wiper relay. Though this process is relatively simple in most cases, specific details might differ slightly between various makes and models of vehicles.

#1 – Locate Defective Relay

Begin by locating your vehicle’s intermittent wiper relay. This relay is typically found within the underhood fuse/junction box, but alternatively, can be housed within a corresponding in-cabin fuse box, depending upon a vehicle’s make/model.

A diagram for relay/fuse identification is often provided on the underside of the lid for each junction box.

#2 – Remove Faulty Relay

Next, remove the faulty relay by hand, with all power disengaged at the vehicle’s ignition switch. If the relay in question proves difficult to remove, a flathead screwdriver can be used to gently pry the offending relay upward.

#3 – Install Replacement Relay

You will now be able to install a replacement relay in the same location that the defective relay was removed from. This is done by simply lining up the replacement relay’s pins with their corresponding receptacles within the junction box, before applying light downward pressure.

#4 – Test For Functionality

With a new relay installed, turn your vehicle’s ignition to the “on” position. Apply washer fluid or water to your windshield first, then test the wipers at various speeds to ensure full functionality is restored. Testing wipers on a dry windshield can cause damage to both the wiper blades and scratches on your windshield.

What Causes a Wiper Relay to Fail?

While relatively durable by design, wiper relays are not immune to untimely failure. Here’s how it can happen:

Normal Wear and Tear – Over time, the internal electrical contacts in the relay can wear down from repeated use. This is especially common in areas with frequent rainfall or where wipers are used regularly.
Electrical System Issues – Voltage spikes and inconsistent power supply can damage the relay’s internal components. This often occurs in vehicles with other electrical system problems or those with failing alternators.
Environmental Factors – Despite being protected by the junction box, moisture and corrosion can still affect the relay’s terminals and internal components. Extreme temperatures and humidity can accelerate this deterioration.
Manufacturing Defects – In some cases, relays may fail prematurely due to manufacturing defects or poor-quality materials. This is more common with cheap aftermarket parts that don’t meet OEM specs.
Excessive Current Draw – If your wiper motor is drawing too much current (often due to binding or mechanical resistance), it can cause the relay to fail prematurely.

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Josh Boyd

Josh has worked as a full-time mechanic for over 12 years, with 6 ASE (Automotive Service Excellence) certifications under his belt. He began his career as an automotive technician at local Toyota dealership and has since transitioned to specializing in diesel trucks and equipment.

3 Symptoms of a Bad Wiper Relay (and Replacement Cost)