The rear wiper on my 2004 pacifica will not spray fluid. The reservoir is full, it makes a noise suggesting a fuse is not the issue, but no fluid comes out- and a full reservoir doesn't appear to diminish in volume. Any suggestions?

Does your front wiper / washer spray?
According to my ALLDATA the front and rear sprayer share the same pump.

First test is to go to the hose coming out of the pump and blow air in it to see if there is an obstruction. If you can blow air through the hose and If you hear the noise and nothing is being pumped out, the pump veins are shot. The motor is turning but nothing is being pumped. It is not real expensive or hard to replace. Get a new pump.

Find the spray nozzle (probably on the wiper arm) and remove the hose, this will be a small plastic hose around 3/16" in dia.
Operate the washer , if fluid comes out clean the spray nozzle out with a small needle and retry with the hose back on.
This may take several tries depending on the amount of gunk in the nozzle.
If the washer will not operate with the hose removed the pump is probably bad, they can make noise and still have a bad diaphragm.

Check hose for clogs if it's ok then you need to check the reservoir motor