Mercedes-Benz W124 cruise control cutting out
Why does the W124 cruise control cut out or not work?
The most common causes are dried-out capacitors and cold solder joints in the control box, the brake light switch, the overvoltage protection relay, a loose speed pulse connector or a faulty pulse sensor. Try the parts one at a time; do not replace everything at once.
In what order should cruise control faults be checked?
1. Brake light switch. 2. Overvoltage protection relay (its solder joints are often cold). 3. The speedometer sensor signal wire connector, which can break loose. 4. Control box solder joints and capacitors.
Where are the W124 cruise control control box and actuator?
The control box is in an aluminium housing on the driver's side behind the lower part of the dashboard, to the left of the steering column; it requires removing the lower half of the dashboard. On the 300 D the actuator is under the intake manifold, and a lever runs from it to the throttle linkage.