How to stop a constraint in position

Hi

Sorry for this noob question, but I'm in trouble working with joints and motor.

For example, I have an hinge joint controlled by a motor. I can apply a force and velocity by keyboard but I need to set in position the hinge when I don't apply any force yet.

In order to do that I'm trying to set the limits at the same value in base of current x rotation like that:

Code (CSharp):

1. void FixedUpdate () {
2.         float l_move_h = Input.GetAxis("Horizontal");
3.         float l_curr_limit = 0;
4.  
5.         JointMotor l_jm = m_hinge.motor;
6.         JointLimits l_jl = m_hinge.limits;
7.  
8.         if(l_move_h != 0)
9.         {
10.             l_jm.force = 50.0f * Mathf.Abs(l_move_h);
11.             l_jm.targetVelocity = 10.0f * l_move_h;
12.             m_hinge.motor = l_jm;
13.  
14.             l_jl.min = -30;
15.             l_jl.max = 30;
16.             m_hinge.limits = l_jl;
17.         }
18.  
19.         else
20.         {
21.             l_jm.force = 0.0f;
22.             l_jm.targetVelocity = 0.0f;
23.             m_hinge.motor = l_jm;
24.  
25.             l_curr_limit = m_cube2.transform.rotation.eulerAngles.x;
26.             l_jl.min = l_curr_limit;
27.             l_jl.max = l_curr_limit;
28.             m_hinge.limits = l_jl;
29.         }
30.     }

...But the rotation seems to be resetted at 0 before the limits application. Can you suggest to me the correct procedure to hold in position the joint?

Many thanks, bye