My van won't start or anything. Battery has been checked and it is fine.

Are your cable ends clean, take them loose and use a wire brush. If you have 2 battery cables bolted to one bolt, you will have to remove spacer from inner cable and clean both sides of it as well. Check cable to the starter, and check grounds at engine block, fenders, etc.

Check for a good power supply,check the ground from the battery to engine or chassis,if the test light illuminates,you have a bad ground,verify the same with the power side,good luck,Rick

Check maxi (big) fuses in fuse/relay box under hood.

Those are known for the braided ground cable between the engine and the right hand frame rail failing and litterally turning to dust. It should be right in front of the right hand engine mount. When you checked for power or the fuses were you using a test light connected to battery negative? While its not the perfect tool in many cases, with a total loss of system power, start with the key on , and or headlights on and start following the power from battery positive, to the fuse block, and then all the way to the engine block. Once you see where you lose power, you'll have to back up to where you do see power, and the problem is "inbetween" those two points.