These roof lifts are known problem children with ageing campers.
There are torsion bars inside the upper tubes that run the length of the camper.
The bars are attached to the brackets in the rear, and to the lift arm at the front.
When the roof is lowered, they are loaded by gravity.
When you crank the roof up, the loaded springs unload and provide lift assistance.
When the lift is all the way up, they are fully unloaded. In that position, you should be able to pull out the torsion bar, I believe to the rear. If I remember correctly, the bar has square ends.
When the roof is stored all the way down, which it typically is for most of the time, the rear brackets are supposed to be level. They are kept in position by the roof structure. But there is a permanent angular force on them from the torsion bar, and when the roof begins to rot, the brackets begin to twist out of their mounting position under the force of the loaded spring.
The torsion bars themselves lose some of their spring properties if they are kept in the loaded position for a long time. You see the same with cars that use this type of spring.
Since there is only about 1/4 turn available to load the spring, both effects combine to reduce the assistance effect considerably, and the roof appears to become ever heavier (well it does when soaked with water) with time as you need a lot more force to crank it up.
Hope this helps, best wishes for your project!
