My washer will not fill with hot water. It will on fill and work when I choose the warm or cold setting. When I choose the hot setting, the washer will not dispense hot water nor will it even work. What is causing this? Please let me know what part to replace, thank you. 
Use a meter to see if you are getting 110v to the hot water terminal on the inlet valves when the machine is calling for hot water. If so, then the valve is defective and will not open. If not, either the timer or the temp selection switch is bad, probably the temp selection switch.
If you want to make sure the valve is ok see if you actually are getting warm water when you make that selection. If so then hot is flowing as it should and the problem is again likely in the temp selection or timer.