Been driving domestics for decades with a low tech metal squeeler that warns you when it’s time to replace pads. My old Audi and now my Maserati are the only cars I have ever owned that had an electronic pad sensor.

Both styles work perfectly fine although the squeeler design is certainly cheaper to maintain.

The pad sensors do go bad from time to time long before the actual pad needs changed and I have even heard of wiring problems so that even a brand new sensor will read CHANGE ME.

 

So yesterday, I braked hard, and the "Brake wear" light came on. Ok, I knew they needed replacing, I have 4 new rotors and 4 sets of new pads in the garage from FD. But on my next startup.... the light was off? I've had many cars with sensors, but all of them, once the sensor triggered (got damaged/cut by the rotor) that was it. Light was on forever unless you replaced or shorted the sensor.

How do the sensors work on these that it can come and go? When I replace with the FD pads, was going to tie them off somewhere, but I figured once I'd set one off, it would need shorted.

Google/forum searches are not returning the answer I'm looking for. Thanks.

The brake pad wear sensor is based on a closed loop system that just looks for continuity. A resistance value is factored into this as well but for the sake of simplicity, there's no need to get that deep. The end piece of the sensor that attaches to the brake pad has a looped wire inside of it. Once the brake pads wear down, enough, the brake rotor will rub through this end piece of the plastic sensor. The looped portion of the wire, inside the sensor, is cut by the rubbing of the brake rotor thereby breaking the continuity of the system and creating an open circuit. This will trigger the light on your dash. You might be experiencing a partially cut wire that is just on the verge of complete failure/teeter tottering with the resistance portion of the system, causing your dash light to be intermittent. But, once your sensor wire (loop) is completely worn through, your dash light will remain illuminated until you replace the worn sensor.

 

The brake pad wear sensor is based on a closed loop system that just looks for continuity. A resistance value is factored into this as well but for the sake of simplicity, there's no need to get that deep. The end piece of the sensor that attaches to the brake pad has a looped wire inside of it. Once the brake pads wear down, enough, the brake rotor will rub through this end piece of the plastic sensor. The looped portion of the wire, inside the sensor, is cut by the rubbing of the brake rotor thereby breaking the continuity of the system and creating an open circuit. This will trigger the light on your dash. You might be experiencing a partially cut wire that is just on the verge of complete failure/teeter tottering with the resistance portion of the system, causing your dash light to be intermittent. But, once your sensor wire (loop) is completely worn through, your dash light will remain illuminated until you replace the worn sensor.
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The way you describe is EXACTLY how I thought my Porsche sensors worked.... till today. Before I posted above about it, I looked it up, as it was 10+ years ago last time I needed brakes (I drive it like 1k to 2K miles a year, if that). Google described the function as I said above, grounding out to the rotor. But when I did the brakes a decade ago I remember it being the broken loop thing. I had just thought I was misremembering.

Either way, neither should really have a on-off mode. Once the sensor is tripped they should stay tripped until you replace it. But I had read multiple posts about the QP that said people would get the warning coming and going. Sometimes for months or years. So I was curious.

I have since found posts that say the FD pads don't have a provision for the sensors anyways, so I think it's moot. I'll unplug them and never look back.

Squeal sensors for the win!

 

Plenty of cars don't have pad sensors..You just check them with a pocket mirror during service..J

 

You don't have to tie anything off, just don't install the sensor on the new pad. Not a wise choice but that's how you disable it

 

Ok. My Porsche sensors have a wire/metal loop in the end of the sensor. When the pads get low, the rotor eats through the rubber on the end exposing the wire, that then shorts to the disk, causing the light.

But normaly once it's exposed, it's always on. It doesn't come and go as you brake. However, the system on these seem to. I've read multiple post about it. Just trying to get my head around why it's different (and if I need to try and order new sensor wires) before I do the brakes.

 

So as far as I know, all these sensors work the same regardless of the make. Sensor is wired to a light and when sensor grounds because pad is low, light comes on. Definitely not a good idea to disable, how will you know when pads r low?

 

The FD pads I got I don't think have the sensor mounting provisions. They are designed to make noise when it's time to replace. According to FD.