No advice to offer, just adding my issue with the same car, a '93 W124 300D 2.5 Turbo. Cruise will engage for a few seconds, then falls out of cruise... Is this the amp or the actuator acting up?

Would also like to know where the amp is located on this car. One guy tells me it's under the passenger's side floor kickplate, another says that on the diesels it's tucked up under the dash, like in older models...