door lock actuator problem

I have installed an actuator to convert my manual lock to a power lock. When I apply power to the actuator it unlocks but when i remove the power it pulls back to the halfway position. The same thing happens when i try to lock the door, it locks but after i remove the power it moves to the middle position. It almost seems like the spring pulling the actuator to the neutral position is too strong for my locks, but I don't know what the problem is. If i manually push or pull the door lock it stays in whatever position i put it and does not try to return to the middle. Any suggestions?

Well normally an actuator will " spring" back from both positions once power is applied and removed, it's normally the rigidness of the actual rod on the door that prevents this, those door lock rods must be really well loosened,  try adding tension to it by tightening!commit your way to jehovah and he will act in your behalf. psalms 37:5

All of the door lock actuators I have seen do not return to center position.  Power one way the they extend and stay there until power is reversed then it retracts and stays there.

it doesn't return to center when it is unpowered and i move the piston manually but or some reason once it gets a lock or unlock pulse it keeps ending up back in the center. I can't get it to stay in the desired position once the power is removed. Adding tension might work but i'm not sure how tightening anything will help? I wonder if the actuator could be trying to move farther than the lock needs to move. maybe it pushes to the unlock position then also flexes the connecting rod causing it to act as a spring?

Take an a new actuator out of the box, you will see it's in the closed or down position. Physically pull it up and it should "spring back". Then place it to your car battery or a 12VDC source capable of 5 amps or more, touch both terminals to power then reverse the connections. the centre section will push and pull then revert to the original position. Are you sure you haven't installed a trunk release solenoid by mistake? Show us a link or the product, also does your alarm have 2 or 6 lock output wires?

well it looks like the problem was my fault. I am using a programmable relay pack for the actuators and I hooked it up in a way other than recommended. I still think it is strange that it was happening but now that everything is properly connected it works fine. Thanks.