Steering wheel moves on its own when turned a third of a turn or more. Pulse back and forth . Have new rack and pinion, steering pump and high pressure line. All the system cleaned and fluid replace.
A faulty metering valve in the rack and pinion can cause the steering wheel to turn by itself. If that’s the case, do not start the car with your hand through the steering wheel because it could turn the wheel with quite a force.
Does your car/truck/SUV/minivan have “conventional” belt-driven hydraulic power steering, or does it have the more modern electronic power steering?
Knowing the make, model, and model year of your mystery vehicle might help to produce some responses that will be helpful.
2007 Buick Rendevous suv. Had 7 rack and pinion in 5 years 4 this year. All were rebuilds from O’rileys
Finally got one from Gm. The the pump was pumping fluid loud . Dealer ship said it would cost to find trouble because the parts were not of their choice no warranty on part or labor claim. Got that on all recent replacements this year. Then went to other shop and they thought it was pump and high pressure hose.
New pump clicked and pulsed. O’riley rebuild and they replaced it. Now the pump will make noise of fluid pumping when I turn and sitting still at light or such the wheel will pulse back and forth and loud pumping of fluid noise. They want to replace low pressure hose now. No need to say this is getting expensive