2004 ford ranger edge blows fuse #20 when you take out of park and put drive. replaced fuse and same thing happens. had truck checked yesterday and found nothing wrong on computer and brakes front and rear ok. transmission is ok. what is my problem.

Check your transmission fluid level. Add if it is low. Your Ranger may at some point need a transmission rebuild. This involves pulling the transmission from beneath the truck and replacing the individual gears. Rebuilds are needed when the gear teeth (the grooved serrated edge of a gear) begin to wear. When this happens the gears cannot engage completely and the transmission will begin to slip.

short circuit in the multi function switch in the column.

Okay, there are a few reasons that this could happen, one being the selector motor which you have replaced so lets go to the next thing which is the fuse, when the motor goes bad it will blow fuse sometimes so check all fuses even under the hood fuse box, i think its a 20 amp fuse but test all of them.

The next problem could be a bad ground, run a new ground wire from the front diff to the frame of the truck.

try these tests and let me know the out come then we can move on, good day, also there is a lot of info on this problem on the web, type in 1999 ranger blinking 4x4 lights, good day

http://www.ford-trucks.com/forums/256814-fuse-panel-diagram.html

It's location is in the fuse/relay box under the hood. It's a 20 amp fuse in position 23.

If the fuse is OK there's a fuel pump shut off switch located under the the glove box just above the carpet. To reset it, turn the ignition switch off, push the button on the switch, then turn the ignition on wait a few seconds then turn the ignition off.

Hope this helps

The diagram you seek is below.

check for a problem neutral switch and wires
may find that switch is loose and grounding out the wire connections or plug

Re check the connections, it sounds like you have a short in the Wireing harness. If you park you car where there are lot's of small animals link mice, squirels ect. They come out this time of the season looking for things to chew on and make a home out of. 
Sorry for the shot in the dark but it does happen and if you do park your car where there are lots of small animals. Fabric sofener's in the car like under the seat keep's them away.
Good luck and hop this helps

you might have blowed blulbs check that also there might be what is called a fuse link in the wiring