HI - upper washer arm does not spray - holes are clear. bottom arm is working perfectly and still cleans dishes on bottom tray. Any ideas?
Here are your parts.
http://www.appliancepartspros.com/partsearch/modelsearch.aspx?model=GU2455XTSQ3
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Check that the flapper valves that cover the 2 holes in the rear water feeder tube are OK.
Give the arm a spin to be sure it rotates easily.
Check the water level after a fill. Most units fill to just under the heating element. If it looks low add a gallon or so of hot water after a fill, just be careful to not overfill it. If the arm now rotates OK most likely the screen filter on the input side of the water valve is dirty.
Do not permanently remove this from the valve as it is there to keep crud out of the valve which could cause a flood.