If it is the same as the'84 to '87's then 2 bolts in the back of the seat ( passenger seat ) each side, with Allan key, remove, then slide seat I believe forward to release the catch that's under the seat.
Remove the seat and the top compartment. It's under the air filter.
Left side of the bike. Remove plastic cover just below seat.
Left hand side. Remove the plastic panel that is below the seat on the side of the bike.
If it is the same as the '85 or '86 models, you will see 1 bolt on each side of the lower part of the seat, they could be the adjuster bolts for the seat to slide forward or back, towards the back of the seat, need an Allen key for this, remove them, the seat will slide either forward or back, ( cannot remember ) Once you slide the seat, it will release from the clip underneath the seat. If you do have no success this way, with the 2 rear bolts removed, peel up the front part of the seat, on the side, you will see on each side 1 bolt, us a wretch and remove them. Should do the job.
Using the correct size Allen wrench, remove the passenger handles on each side of the bike. Then, lift the rear of the seat up and pull rearwards after it clears the passenger backrest.
Left hand side below the seat. Remove the plastic panel to access the battery.
There are 2 Allen key bolts at the rear of the seat. One on each side, just above the shocks. Remove them, then push the seat forward so that it will slide out of the clip under the front of the seat. If you cannot slide the seat, then there are 2 more bolts around the middle of the seat tucked up a little. Then remove them.
The 1200 and 1500 had a seat height of 30.7" until 1995. They lowered the seat height to 29.1" in 1995.
You need to first remove the plastic panel behind the seat above te rear tire. It is held on by a single screw. once this is removed 2 screws will be exposed that are holding the seat in place. Remove them and your all done.
You have to use your key to unlock the helmet holder, then push seat backwards to lift out of slots.
The only seat adjustment that I know of is forward or backward. There is a pin you pull at the rear of the seat, and it will slide. As for up or down, there is none that I know of.
The fuse box on a 1981 GL1100 Goldwing is located under the seat near the battery. It is sealed in a water tight box to prevent damage.