most likely the rear window wiper has not retracted or returned to the proper UP or NOT IN USE type position so manually help it back UP until you can research repair or replacement of window assembly motor or perhaps replacing the magnet part that keeps it in that UP position. that's what i am learning still and may your window roll up when the rain comes down!
Rear window relay is inside the pillar on drivers side - its easiest if you remove th rear passenger interior side panels
Check your window lock switch.
where is the rear window defroster relay located in a 2004 Toyota Four Runner, would this also control the rear wiper arm? Try something simple: just open and re-close the rear window. The window has a safety switch that keeps the wiper, washer and heater from working if the window is open. The window settles down (from opening and closing the hatch) over time the window settling triggers the switch. If you open and re-close the window it resets the switch and everything works again. My 2003 4 Runner does this over time. I just open it and re-close it to fix the problem.
Could be a few things. Can you row it down using the key on the hatch? I have a 93 I can open and close with the key but the rear window sitch wont roll it down only up. I suggest you replace the switch I cant imagine it being more than $15 new or maybe cheaper from a salvage yard The rear window will only go up and not down under normal conditions if and only if the windshield wipers are on. Also the key fob only allows the window to go down not up. You can use the key in the liftgate to make the rear window to opperate up and down. If the switch in the dash has warn-out, you can have it replaced at your dealership for cheap.
The front and rear washers share the same reservoir, which is located under the hood. It holds a gallon of fluid.
The 2004 Toyota 4Runner has 57.2 in. of rear shoulder room.
The 2003 Toyota 4Runner has 34.7 in. of rear leg room.
The 2007 Toyota 4Runner has 34.6 in. of rear leg room.
The 2004 Toyota 4Runner has 55.3 in. of rear hip room.
The 2003 Toyota 4Runner has 57.2 in. of rear shoulder room.
The 2014 Toyota 4Runner has 32.9 in. of rear leg room.
The 2009 Toyota 4Runner has 34.6 in. of rear leg room.