dweller,

The new vacuum units can't be rebuilt as they're sealed. However, if you can get one of the older units and install it they can be rebuilt just by installing a new diaphram. You may have to drill new holes to install the older model. I collect the older units and when I have a complete set, I retrofit one of the family's newer 123s. The older units actually move the door locks up or down faster as well. If you check prices, you'll see the five dollar diaphrams are much cheaper than the new sealed units.

Ben