Mainly older coaches have a soft roof construction. This kind of roof was typical a few years back, using wooden or metal rafters over which the exterior roofing metal was rolled and installed. Fiberglass insulation was laid between the rafters.
Some roofs had a thin layer of plywood secured to the rafters and then the roof metal on top of that, but many simply had a thin layer of sheet metal loosely rolled out over the rafters. The result: no support between the rafters. While working on the roof, the technician or RV owner can only step on the rafters or position a longer walking board across two or more rafters. Water leaks are very common with this type of construction, as any step between the rafters would disrupt the sealants on the seams and edges of the roof. The added weight of air conditioners and storage pods also contributes to water leaks. Today's roof technology involves sandwiching a much stronger layer of foam insulation between multiple layers of plywood, sheet metal and, in some cases, a rubber roofing material. All moisture is vacuumed out of the roof and special glues laminate and bond all the materials into a very strong, self-supporting component. To solve your leak problem and to raise your air conditioner, you will have to discern how far apart your rafters are.
This is usually easy to determine by just looking at your roof. On most soft roofs, the rafter positions are evident. Measure the distance between the centers of the rafters. It will usually be 16 or 24 inches. Some, however, are spaced at 20 inches and I have seen a few at 12 inches. Next, you must remove the air conditioner and RV cover.
Mostly few years back all air conditioners were basically sandwiched to the roof by the use of three or four mounting bolts. Here's the procedure. First -- and very important -- order a mounting gasket for your brand and model of air conditioner from your RV parts store and have it in hand before starting. Most gaskets and seals will be ruined when removing the unit. Next, disconnect the 120 volt AC power to the RV. Remove the ceiling plenum or air distribution vents on the ceiling. Refer to the owner's manual for the details.
After removing the lower plenum, locate and remove the mounting bolts. At this point the air conditioning unit on the roof can be safely lifted and set aside. Take care when lifting the unit off the roof. Old sealants may cause the unit to stick to the roof metal, which is easily torn. What you now have visible on the roof is an indentation where the air conditioner used to be and a hole about 14 inches square. Be sure to clean off the old gasket and any sealant from around the hole. Next, cut a piece of 1-inch plywood 28 inches wide by however long is necessary to span two adjacent rafters on the soft roof, making sure the 14-inch hole will be inside the plywood area.