I bought a 83 Quantum about a year and a half ago and ever since I have not been able to get the locks to work on the doors or trunk. I have lived with it but it gets old not being able to lock the car!! I cannot push the door locks down from the inside and the key is very hard to turn on the outside, so I do not force it. It is this way on the trunk and front door. I can feel it start to turn, then it gets very stiff, I know they are the right keys!! Any idea what this might be? Does this car have a central locking system?