Sunroof question

Hi,
I have a 1972 911S with a sunroof. The sunroof works, but when you press the switch to open or close the roof, the motor does not stop until you take your finger off of the switch. I was under the impression it would work like the power windows, close or open, and stop when it is fully opened or closed.

Any ideas as to where the problem is? Is it the motor, or am I missing some part.

Do I need to replace the motor, or can they be rebuilt? What would be the correct part number for the motor?

Any help is appreciated.

Thanks,

Marc

The car is 50 years old , the motor does not stop automatically .

the same thing happens in my 72, you have to keep it going for the full route... it's normal