Brake Wear Sensor Question

Does anyone know how the break wear sensors work? I know it's just a loop of wire stuck in the pad. But when the pad wears down to the point where the light comes on, how does that happen? Does the rotor wear through the wires and break the circuit, thus turning on the light, or does the rotor wear off the insulation from the wire and then MAKE the circuit, lighting the light? Two more quetions: to reset the light (once I've replaced the worn pads), do I have to do it via OBDII, or not? And finally, if I want to just remove the sensor wires and not worry about them, can I just unplug them at the connector on each wheel, or do I have to leave the plug in with a short in it, to simulate the sensors being present? (I would think that would be the case) OK, you brake experts, let me hear from ya! Thanks, =Carlos=

You are right on the money the plastic part gets worn down when you have gone through a % of the pad. When the plastic is stripped the two wires make contact the sensor light is triggered. Not really high tech but it's a great security measure. Why pay for new rotors if you do not need them. If you get to the point of metal to metal contact it is going to cost you a set of pads and rotors. I say replace the sensors if they were damaged. They are cheap compared to a new rotor or set of rotors.

Well another thought is......they're a pain in the butt.........I tied mine back out-of the way a couple yrs ago. I'm thinking you really should know 'about' where your pads are......kinda like where your tire presure is at. If you change pads frequently for track weekends it's a 20 minute job tops (but 45 if you have to mess with the sensors every time).......and if the street pads are in your hands, well you know what shape they're in .

This is one of the better questions I have seen here in years. I though it was only the first event. But I have been told it can also be the second.

I agree. I did the same thing (tied the sensors back) w/my 986.

The sensors are "fail safe". As the pads wear the sensor surface also wears and at some point the wire (loop) internal to the sensor wears through causing a loss of signal to the computer and a fault is seen. "Fail safe" means that any loss of signal, broken wire, bad connector connection, etc. will initiate a fault and not allow you to not know if the system is faulty and continue to drive till damage is done. Hence the name "fail safe" condition. I've saved a couple of old ones and cut the wires short and tied them together making a short jumper and plugging them into the connector. Same as tying the OE ones back, just a bit neater.

Thanks for the feedback so far, everyone. So, it looks like the circuit gets broken when the rotors wears through the wires, and then the light lights. That kinda fits with what I thought. Now about the other part to my question, does resetting the light require access to the OBDII port, or will it simply go out as soon as I replace the sensors? (Actually, I think I'm going to bypass the sensors completely, and just put in a shorting plug, as someone else mentioned. That makes sense for me, since I track the car and check/change the pads frequently. But I still want the light out...) =Carlos=

Carlos, I had originally tied the wires to the sensors out of the way when I switched to track pads, but months later got a "Pad Wear" warning light. I assumed something had come apart in the wear sensors, so I cut them short and connected the wires for all of them, as I had done successfully with my 928 S4. Unfortunately I still have the warning light most of the time (not always, interestingly), and would love to eliminate it, but not if I have to go to the dealer to reset it. So does anyone know if that is the only way to eliminate the light once it has come on? My interim solution has been to apply a small round piece of electrical tape over the light on the dashboard...hardly noticeable except in the right (wrong) light! Scott

Carlos, They are cheap and they are very easy to replace. I have done them on my 2000 996 recently. My light simply went out upon completion of the job, and has not come on since. There was no reset done, no dealer involvement at all. Work with confidence, solve your problem and enjoy your car! Bob

Just pull the cluster off and pull the bulb from the dash completely. It's really a 30 minute job but it also doesn't look like crap (tape on the dash). If you have any quesitons on the DIY, let me know. -Eli

About 20% of pad is left after you hit the wear sensor. As the pads thin out they heat up faster and in turn heat up or even boil your brake fluid. So keep an eye on your pad thickness. I always tie my wear sensors out of the way for the track pads and re-install with the OEM pads. Very easy.

OK, it sounds like the light should go out on its own, once the sensor plug is shorted out. I'll probably fool with it this weekend and see how it goes. I live in a state that requires a yearly safety inspection, including brake pads, and between that and several DE's a year there is NO chance of the pads wearing down without my knowing it. Specially now that I'm going to be swapping out the street pads for Pagid oranges for the track events. So I really don't need the sensors, and they do slow down the pad swapping, so I'll just bypass them. I'll report back on how it goes. Thanks for all the feedback from everyone. =Carlos=

Carlos, Another thing to check is the housing into which the brake sensors plug. I melted mine once at Watkins Glen, which caused the brake warning lights to illuminate despite the fact that the sensors themselves looked like they should have worked. The dealer asked me if I had tried to silicone the sensors in place until we realized what had happened. At that point, I did two things: 1) I installed the GT3 RS brake scoops and 2) decided that I needed to learn to momentum drive as if I didn't have brakes, so I bought a 944. Once I learn to drive the 944 well, I will return to the world of high HP. TD

TD, where did you source those brake ducts from? I've thought about this too, another thing that might work is fenestrated inner fenderwell from a C4S which directs more airflow to the brakes. I've seen melted sensors before as well, C4S Surgeon had like 3 of 4 sensors melted when we did his brakes. The excess heat can come from heavy braking on a high speed track w/ OEM pads, thin pads, spent brake fluid, or all of the above.

Mine was old fluid that boiled,scary stuff.

Doug, I got mine from Suncoast: http://e-partssales.com/Merchant2/me...Code=996brakes I altered them a little to direct the air flow more efficiently. They snap right on with no tools necessary. I have had no problems with tires rubbing on them, although I have heard some people do. I was using stock brake pads when I melted my sensors. I moved to PF after that. I am back to stock now that it is a street queen. TD

Eli, How hard is it to remove the cluster to get at the light? Is it really just a 30 minute job? Do you know of a good write up on how to do it? Scott

Scott, I have some photos that I have ready to put together a tech artical for the site, I'll shot them over to you if you promise not to repost them..... Sorry I haven't done the write up yet but I can walk you through if you have questions. About 20 photos in all.... [email removed] -Eli

Removing the cluster is not hard. We do it all the time when we retrofit the OBC because you need to add 4 wires to one of the connectors on the back of the cluster. There are lots of Boxster instructions out there. The only difference with a 996 is that a 996 has the oval trim piece around the hazard switch that a Boxster does not have.

Thanks, guys. I'll give it a shot. Gona miss the electrical tape, though. Scott