Brand new washer, 2 days old, but messed up on day one! It seems to get stuck in between cycles! Water half fills, then empties, and it will not go into the rinse cycle!

Either the fill valve is not working or the controller is not sending a signal to fill valve to open. If parts needed check here Search Over 2 1 Million Appliance Parts

If you have hard water in your area, the valve could be stuck in the open position. Try running an empty cycle and see if it stops filling. Either way, you may want to follow manufacturers' instructions for de-liming. If this fails, the valve/solonoid may need to be replaced.
Best of luck.

There are electronically turned on and shut off water valves that are controlled by a water level sensor which varies based on what load size/water level you need Small, Medium, or Large. So if the valve gets stuck open since it's an old machine, the water will just keep coming in. But let me ask you this? If you turn the house water value on n NOW...will the wash machine just start filling? If so, it means your valve is stuck open so you would need to replace the water valve which is like $50 online. If the house water valve is on, and when you start the washing machine it starts filling, but just keeps on filling...that's probably because your water level sensor is messed up. So you have 2 things to check...is it the washer water valve is stuck open? or is it the water level sensor that isn't sensing when the washer is full so it just keeps filling it.

Could be a problem with the water pump

Possibly your problem is the tube that tells the machine when the water is full. It may be blocked.

Does it fill with HOT water (check after fill stops)? Did Sears install the washer? If so, have them troubleshoot the problem. It's obviously bringing water in. Are there any error lights or codes? May need to replace the control unit.

brand and model number

It sounds like the water inlet valve needs to be replaced. The solenoid which opens and closes allowing water to flow or not flow, seems like it's stuck open. What brand washer? & Model? I could help you find the correct part. They aren't usually too expensive & if you love your washer, it's not worth buying a new one. :-)

the main water valve that the fill hoses connect too in the back of the washer is probably bad.

The fill valve may not be telling the unit that it is empty. Try pushing it down and see if it will restart.