If the car stacker was on the original strata plan, then your lot unit entitlements reflect the lower value of your lot compared to others that have a parking space. Thats the theory anyway.
Therefore the levies you pay compared to someone that has a parking space is less. So whilst your levies do go to maintaining the car stacker overall you are paying less levies than others (with a car space)
If the car stacker was installed after the original strata plan, then there SHOULD have been some account in order to make those who benefit from the stacker pay more.
Also check that the car stacker is common property. If it is not, then you ceratinly should not be paying for any maintenence and running costs for it.
Trying to change what you have now is going to be very costly and difficult.