right signal not working

Say that again, really slow? You moved working bulb into the socket, and it doesn't blink. So, the wiring is OK? I must have read that wrong.

On a van that old, think "bad ground".

Put the four ways on, and walk around to find the bad one (a tip you don't need cause you already knew).

Remove the bulb and check the inside of the socket very carefully. Clean it up real good. If it still doesn't light the bulb, jiggle the bulb around a little to see if it makes contact and finally goes. The insides of the socket can get all crapped up and have a hard time making good contact. You might have to pry out the contact strips a little on them. They even wear down a little over time and may need to be pried out so they make contact with the bulbs.

sticks

These are all good suggestions. If none of the above work, try replacing the entire bulb socket. I have a 1998 Chevy Tahoe and the dealership said they've had lots of problems with these. I've had to replace mine two or three times. They're easy to replace yourself.