My ASD light has been permanaently on for some time. I am not experiencing any problems. New legislation in UK means that I will fail my MOT test and have to take my car off road. Anything to do with the brakes is a serious failure in UK and I am not allowed to drive it, even home from the MOT station and if I do will risk getting a £2000 fine and points on my licence or maybe taken to court and banned. My mechanic does not know what to do. The car's diagnostic system is the first ever introduced by Mercedes in 1984 being the 8 pin (X92), which is flash/blink. I get 8 blinks and the fault is listed as Magnetic valve or brake light switch. The brake light switch has been replaced. The light went off for about 1 month and then came on and stayed on. As the car is so old I cannot find a mechanic who has had experience with this problem and knows how to resolve it as most mechanics rely on computer diagnostic tests. Can anyone help. My mechanic is trying to get a schematic of the ASD electrical system to start with but has no knowledge on this problem.