Mercedes-Benz W126 ABS and ASD lights on because of low voltage
420 SEC300 SE
Why are the W126 ABS and ASD lights on?
The lights can come on when the system voltage stays too low. Reported causes are failing solder joints in the overvoltage relay (YJ relay) or a fault in the alternator regulator. The cause varies from car to car, and it cannot be found by guessing alone.
Can a faulty YJ relay on the W126 turn on the ABS light?
Yes. A bad solder joint can heat up and let too little current through, so the voltage drops briefly and the lights come on. A relay that looks new on the outside can still be faulty, so the relay's solder joints should be gone through.
What should be checked first when the W126 ABS light comes on?
Check the battery charge, the charging voltage and the connectors, because oxidised connectors cause the same symptoms. If the fault is not found, have a workshop investigate. ABS is part of the brakes, and brakes are safety-critical.
Related articles
Mercedes-Benz W126 heater blows only hot airMercedes-Benz W126 heater not heating or heat disappears while drivingMercedes-Benz W126 K-Jetronic cold start injectorMercedes-Benz W126 runs too rich: causes and lambda sensor checkMercedes-Benz W126 fuel pressure regulator and pressuresMercedes-Benz W126 clogged and leaking fuel injectorsMercedes-Benz W126 idle speed and high idleMercedes-Benz W126 auxiliary air valve and idle control valve