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You are watching: How to reset brake warning light on mercedes

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neurosoup.org Mercedes-Benz Forum > Mercedes-Benz tech Information and also Support> Diesel Discussion
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W123 dash brake warning lights, a review
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Lets evaluation the W123 brake irradiate warning system. In the dash, there are 2 warning lights connected with the brake system The first and most necessary is the Red " BRAKE " irradiate in the dash. ( snapshot #1 ). This light has actually 2 functions. It informs you that the parking brake is involved and an ext importantly it informs you that the hydraulic brake system reservoir liquid is in ~ a low level. The mechanism uses a wire schematic that you can see in picture #2. From the #12 fuse, the circuit goes come the warning irradiate in the tool cluster. From over there it travel via cables to both circuits in the brake fluid reservoir and then come ground G102 i m sorry is located behind the instrument swarm . The black color buttons at the optimal of the reservoir are test buttons for the floats in the reservoir."Reseting" them together is sometimes posted, is not quite what you room doing as soon as you push the button. If the irradiate is grounding on and is brought about by the float. When you "reset" that you space trying come disconnect the float indigenous the reduced "on" contacts. This is whats resulting in the false ~ above indication. The rise ( picture # 3 ) might be gaining old and not move up and down freely. The larger cars have actually a single chamber system and only 1 float and test button on height of the reservoir. More recent models have the twin chamber reservoir and 2 black buttonsThe second circuit that the Red " BRAKE " irradiate goes come the parking brake pedal assembly and also lets you recognize when the barking brake pedal is in any type of position other that completely back ( parking brake turn off ) snapshot #4 mirrors the company Manual diagram of the switch location. To check the 3 circuits because that a error ( definition your irradiate is ~ above ) you just disconnect the cable harness going to the reservoir float or parking brake switch one in ~ a time and check the light. If the light goes out, then it is that certain circuit. You deserve to replace the parking brake switch yet the reservoir switches cannot be replaced. A brand-new reservoir is required. Yet the black color rubber caps room available. The course very first make certain that both reservoir sections space filled v brake liquid to the "MAX" line. Come look at the behind chamber it is ideal to look on the passenger next of the reservoir towards the ago of the reservoir. I generally wiggle the reservoir side to side, it provides it simpler to view the liquid level change.A 2nd light in the dash is because that the front brake pad undertake warning device ( photo # 1). As posted, the stay sensors space in the former pads only. 2 wires per wheel, one in each pad. The electrical circuit ( photo #5 ) goes native the #12 fuse, come the instrument cluster strength line, v the warning pear to the 4 sets of sensors. Then to the G102 ground for the left former hand wheel and the G101 ground for the best front wheel. The G101 floor is situated RH prior fender behind the headlights. Interestingly enough, the wear sensor speak you the your pads room worn the end by grounding the circuit ( actually completing the circuit) once the plastic covering of the undertake probe sensor is floor away and also the exposed probe cable touches the rotor ( the is why the flickers originally ). Ns actually have actually not watched the cable for the wear sensor as it goes to one of two people G101 or G102 as presented in the electrical schematic, go figure. Over there is no a wear warning mechanism for the rear pads or the parking brake shoes. Girlfriend should examine the rear pads because that every 3 prior pad replace instead replace ( not a negative idea to examine them every 2 set of front pads ) The parking prake shoes have to last rather a lengthy time, i personally have never replaced a set of parking brake shoes in all the Mercedes I have owned (9 at critical count). To prevent from replacing parking brake pair of shoes you have to keep the parking brakes in adjustment and also not drive the car with the parking brake on. I hope this helps anyone that has any questions about the dash brake lights. Dave


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Great post - btw, where would I discover the small black plugs that cover the vent/circuit testers - mine room cracked? Fastlane hopefully?