Turning off brake pad warning on 2001 S320?

[television]

fellas
my calipers only have one sensor contact

i assumed that the brake warning light system was open circuit until the disc wore the pad away enough to touch the sensor probe thus providing an earth and completing the circuit

did i get it wrong?

You are 100% right

 

[television]

I am so fed up with the wrong post from eric, see number 20 here

Just to get some backup on what I have said in the post above, I am happy to send a sensor wire to anyone with a meter that can check that there is no circuit until the plastic has been worn through by the disc.

Please some help from someone on this.

 

[type49]

Yes, there is no circuit, or "open circuit", until the sensor has been cut through & earthed out by the disc.

 

[television]

Yes, there is no circuit, or "open circuit", until the sensor has been cut through & earthed out by the disc.

Thank you very much again Type 49.

 

[television]

Just to complete this thread, somewhere along the line a guy had his sensor light on all of the time, so I will explain how this circuit works.

The lamp that lights when the sensors in the brake pads touch the disc, now this lamp circuit is known as a self latching lamp, that is, once the circuit is complete and the bulb lights, there is a relay that stays locked on during that ignition cycle. This means that if you start off in the car with pads worn beyond their limit, the lamp will not turn on until you press the brake pedal completing the circuit once again, and the lamp will stay on until the key is turned off. The it starts all over again until new pads are fitted.

If you take the sensor wires off and the lamp stays on, either the cables going to the sensors are grounded somewhere or the latching circuit on the warning lamp is faulty

 

[sixpack]

Brake wear sensor

Hi Malcolm,

If the sensor just shorts onto the disk when the pad wears, why are there 2 wires connected to the to the sensor ?

Peter

 

[type49]

SIXPACK

Some later models use a closed circuit & when the disc cuts through it, it recognises an open circuit & puts the light on. The car in the original thread doesn't have the same circuit as your 203

 

[television]

Thank you again type 49, I have just been reading up the differences on all of the car and the different types of sensor.It is a jungle with all of the different cars and features.

with the type that go open circuit there is no latching circuit needed for the lamp as once the sensor has been cut the lamp will stay on until a new sensor and pads have been fitted.

This also shows the dangers of someone joining a thread with a different car, but the same fault.

 

[sixpack]

Brakes

Hi Malcolm,

So how many wires go to the pad wear sensor on a 2001 S320 ?

Peter

 

[hmang]

one mate
the system is open circuit till the pad wears down to the sensor which then contacts the disc,completing the circuit and the warning light comes on.

 

[eric242340]

one mate
the system is open circuit till the pad wears down to the sensor which then contacts the disc,completing the circuit and the warning light comes on.

There is one very simple test to determing which system you sensors are working on. Disconnect one brake pad wear sensor and see if the light comes on. I guarantee on 90 percent of models it will come on. This is the computer checking to see if the sensor is there and responding. Especially 2001 S320. The sensor, itself, has one wire and the cable going to it has two.

 

[kth286]

There are pads on each side of the disc.

I therefore guess a sensor is required for the pad each side for safety.

because in the case of a faulty/sticking caliper where one side pad was worn down to the limit but the other was not, you may not get the warning light on.

 

[television]

There are pads on each side of the disc.

I therefore guess a sensor is required for the pad each side for safety.

because in the case of a faulty/sticking caliper where one side pad was worn down to the limit but the other was not, you may not get the warning light on.

If you look at the chart Keith on WIS some cars do,some do not, some use 3 sensors dependent on the car spec, some brake pads have 2 holes, some change several times like on mine, My car does not use rear sensors,the AMG do.

It really is replace what you find, the bit that I could not get through to Eric was that if you unplug the sensor end from the pad,it had no bearing on the light being on or off as the Pads are non conductive.

 

[hmang]

malcolm
i think eric is talking about disconnecting the sensor at the caliper rather than at the pad

 

[television]

malcolm
i think eric is talking about disconnecting the sensor at the caliper rather than at the pad

The only snag here is that he will claim to have meant that,now that you have said

 

[television]

There is one very simple test to determing which system you sensors are working on. Disconnect one brake pad wear sensor and see if the light comes on. I guarantee on 90 percent of models it will come on. This is the computer checking to see if the sensor is there and responding. Especially 2001 S320. The sensor, itself, has one wire and the cable going to it has two.

There is no computer checking, and 90% of cars use a single wire and nothing will light if you take the sensor leads away.

So even this is wrong, You could well be a very nice man eric, and i do not doubt that, but for once in your life Just tell us where this computer is or if it shares another one, on this S320 especially as you say

Now is your chance to prove where it is and restore your name. being a MB training center you must have more info than me

 

[eric242340]

Malcolm, make it easy, go to your car and disconnect a brake pad sensor and then start the engine and push the brake pedal. The warning light will come on. I totally agree with your post on the sensor working on a ground and I have said that on this thread. But what you dont see is the newer models 1999 onwards have a system inbuilt to check if the sensor is there or not. Which control unit checks with the pad sensor varies from model to model, ie Models with SBC or ABS or ABS/ASR or BAS. But whichever control unit is doing the test, it sends the signal (good or bad) via the engine control unit to the IKE ( instrument cluster). I hope im not going to get another slagging for this post? Can we not simply discuss things without this.?

 

[television]

Just to close this thread most of us are agreed that the single wire sensor can be taken off and left off if one wanted to do this. This is the one shown in picture 1. This is known as a open circuit type

Talking to a service manager today, he said that many garages do not fit new sensor wires, and MB changed the type over to a two wire system (picture 2)this means the the two wire type must be plugged into the chassis socket, but one could still cheat as you do not have to plug it into the pads, you could if you wanted to turn the light out, just twist the wires together to stop the light coming on. This is a closed circuit as agreed by most of us earlier in this thread.

There is no computer re set for any model MB brake pads light and this circuit is not part of any other control unit on the car

How many pads that are wired in varies from car to car, this is nothing to do with ESP,ABS or anything else. You could if you wanted add more sensors as they are joined in parallel. The normal way is to replace them where they were. If any one ever gets stuck as to how many they should have, just ask

 

[television]

Anyone reading these threads must ignore number 37 by eric 242330 as it is totally wrong, and was posted purposely by eric as a wrong answer.

The brake pad sensors are a circuit on their own and not part of any computer,ECU or control unit on the car.