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Brake Pad Sensors: How They Work And How To Fix Them

A brake pad sensor on a car. A squeal isn't the only way to know it's time to change your brake pads. Brake pad sensors also let drivers know when it's time to change worn-out-brake pads. Here's how they work.

Brake pad sensors might seem like new technology, but they’ve actually been around for quite a long time. In the early days of motoring, it was simple enough to communicate to drivers that their pads needed replacement by attaching a metal tab that would eventually make contact with the disc brake rotor after enough wear had occurred. The unpleasant squeal meant that it was time for a new set of stoppers.

How have disc brake pad sensors changed? Let’s take a look at the technology.

Quieter Electronics

Clearly the irritation of squealing brake pads wasn’t the most driver-friendly way to indicate an issue. This is why electronic brake pad sensors were developed. Instead of using friction to create sound, they used a wire with an electrical current. When this wire came into contact with the brake rotor — after enough pad wear had put it in a position to do so — it would illuminate a light on the dashboard indicating it was time for a pad to be changed. Some systems used a two-wire setup, with varying degrees of pad thickness triggering a multi-stage warning by breaking the circuit earlier on in the pad’s life.

Naturally, the urge to complicate things arose, first in the luxury segment, with some vehicles offering a pad life calculation based on the mileage used to reach the first wear sensors. Some systems even factor in things like brake temperature, driving style, and even brake pad material into that equation.

Replace, Not Fix

You might have picked up on it by now, but when using terms like “break the circuit” to describe how a particular sensor works — especially one that’s related to wear — it’s typically not possible to use that particular sensor more than once. Brake pad sensors are intended to be replaced once they have served their intended purpose.Brake Pad Wear Sensor

Some pad sensors are built directly into the pads themselves, while others are an add-on item that is changed when the brake pad itself is replaced. Installation of these sensors is a relatively simple process, and you don’t have to go to your dealership to find a set that will work for your vehicle. There are a number of aftermarket or direct-replacement brake pad sensors out there that fit a wide variety of vehicles.

If you’ve got a brake service light illuminated on your dash, it’s not something you should ignore. Believe the sensor — or the squeal — and have your system serviced as soon as possible so you can stay safe out on the road.

Check out all the brake system parts available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on brake pad sensors, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Image courtesy of Creative Commons.


Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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