Brake pad sensor...how does it work? repair?

[yardbuzzard]

My 94 ls400 rear brake pad sensor has broken. How does it work? Is it just two wires that are cut when the pad wears down so far as someone on this site stated? Or is it part of the abs system and must be replaced rather than be repaired by soldering together?
any help, ideas would be appreciated.

 

[Zuffen]

Most brake pad sensors are just two wires sitting in a carrier.

When the pad wears enough the sensor makes contact with the disc which completes the circuit (make the power flow from one wire to the other through the disc) which then illuminates the warning light.

Be very sure you are only dealing with the pad wear sensor. The pad wear sensor will be attached/inserted in the brake pad proper.

The ABS will be a separate sensor aimed at aring od notches in the back of the disc.

 

[yardbuzzard]

thanks for the reply
So the disk becomes a ground and breaks the circuit and the warning light comes on?
IF this is true, if the two wires are cut and then soldered together, the brake wear light should not come on?
I dont really see any need for this wear sensor in the first place. The pads on my car were nearly to the metal and no warning light was on. Just need to check more often on my part.

 

[Zuffen]

The disc doesn't ground the wires. If it did you would/could get erosion in the bearings due to passing the 12volts through them.

The disc completes the circuit between the wires. Usually the wires will be on the earth side of the warning light so there isn't a short circuit through the disc to earth.

If the two wires are cut and joined the light should stay on.

If you cut them and leave them separate the light will stay off.

The sensors are to alert drivers they are almost out of pad. The light only comes on when there is very little life left in the pad.

 

[yardbuzzard]

thanks
you told me what I need to know. cut the wires, protect the ends...no more sensor!

 

[mrsmall82]

sorry for the late response...actually,each sensor is a closed circuit.When the pads do wear down far enough,it allows the rotor to eat away the breaking point of the wire and set off your brake pad wear indicator.Look for yourself,it's attached to the pad.

 

[yardbuzzard]

thanks,
The reason I have asked is that one wheel sensor line of my car is cut into right at the sensor. I have soldered them to the sensor and the light is not on. But I am afraid the repair will be temporary. Rather than replacing with a new one, I was trying to come up with a fix. If the circuit is kept apart as you suggest, it should not matter if the sensor is attached to the pad or not? Of course the pads will not be protected but more timely inspection is in order.

 

[mrsmall82]

no sir,it does not matter if the sensor is attached to the pad or not.It's not really a sensor like magnetic ones or even temp sensors.Its just a wire that breaks when pads are worn down far enough.Rather than going to lexus to get this part,forgetting about changing your pads and have the same thing happen again...just cut it and solder or tape the ends together and you should be okay.As long as the wire doesn't get a break in it again you shouldnt worry