Polaroid Sun 660 problem

I need help with one Polaroid sun 660.

It seems that auto focus is not working at all. After investigation on internet i noticed that this camera has a 4 disc lens , so every time that you press the shutter button , sonar calculates and the camera chooses the right lens for the given distance. In my case all photos are blurred and pressing the shutter button ( using flash or not ) the internal lens are not moving.

I was searching for a repair manual or instructions, but unfortunately i cannot find such documents. Please advice if you know how to repair this. Removing the front cap i was not able to correct the problem. Probably i have to go deeper, removing more parts of the device but, without advice or repair manual i will never be sure what i am doing there.

Just to say that it is not related with power – i have used different cartridges and the problem persists. Thanks!