1998 terex tb60 cummins idle

[wookiee]

Ever since I had the local tractor shop do an oil and filters change my Terex Cummins 4B3.9-C runs rough at the 2nd of the 3 rpm settings (low idle, mid, high) and eventually drops to low (and smooth) idle.
I bled the system.
When I hold the actuator (2 years old) in the correct position it runs fine. The Addco controller module, which controls the actuator, flashes yellow and green then RED as it drops down to low.

Where does the Addco get it signals from?
The actuator mount looks like something is missing. It's just hanging by the shoulder-bolt. Is there supposed to be a rubber shock pad between the mount and the actuator hanger?

 

[Knepptune]

Basically the addco has three settings. Neutral,mid and high. At idle the controller isn't getting any signal. Most have a spring to naturally return the engine to idle when the controller is off. Mid it just gets voltage to one wire. I forget the colors. The actuator moves to a set position. As the actuator extends or retracts the resistance changes. Basically when you install one of those you set the how far you want the actuator to extend at that setting. If it's at mid range it just extends the actuator to that same point every time. If the resistance is not consistent it'll confuse the controller. It can also cause the actuator to hunt because it's looking for the right resistance reading. if it's flashing red it's getting signals it doesn't understand. It's been awhile but basically you unplug the controller from the actuator and figure out which two wires are reading resistance. Just check the ohms across the wires as you move the actuator in and out. Its make take just a minute to figure out which two wires your looking for but the resistance should be smooth and consistent. If it jumps around at all your actuator is on its way out.