WHEN U SAY THE WATER SWITCH IS GOOD Have u dont a voltage test as well as a OHMS meter reading? As it can test good for ohms and still be bad electronically. the only other thing to check is the water pressure switch but my bet is with the water inlet valve or bad control board issue
Washer fills with water and overflows:
The water pressure level switch is a pressure activated switch that is used to determine the correct water level in the tub. This part is normally located behind the control panel and will have a hose or air dome tube that connects it to the tub. On washers that use an electronic control, this switch may be located at the sump area below the tub. As the water fills in the tub it will compress the air in the tube and push against a diaphragm inside the switch. The switch will control the water inlet valve and turn the valve off at the correct water level. If the tube has a leak, not enough pressure may be created to activate the switch and the washer may overfill. If the switch is defective it may also cause the machine to overfill. To determine if the switch is bad, you should first eliminate the air dome hose as a problem. Look for signs of cracks or worn areas on the hose. Remove the hose and submerge in water. Seal one end and blow air into the other end and look for bubbles. Check for an obstruction in the hose as well. If the air dome hose appears to be ok, then the water level switch may be defective.
You can test it with a meter and with a manual test? ( first locate it in the panel, it has a plastic clear tube hose going into it, remove that tube from its connection, now put another small tube or hose into the slot where it was and have the machine set to wash cycle with water in it. Blow into the other end of the tube.
If the machine starts to wash. the pressure switch is more than likely good
( No wash- then THE DIAPHRAGM IS BAD AND SWITCH HAS TO BE REPLACED).
The other item to check would be your water inlet valve. Check it for continuity with a multi meter it should show Ohms or a closed circuit. To test it when water is overflowing unplug the unit and see if it still overflows or continues to fill. If it stops when unplugged. Then it is not a water inlet problem but an electrical signal problem going to ur water inlet valve. Possibly from the panel or board. You can also do a live volt test to see if it is getting the full 120 current, but be sure to unplug unit before testing as this is a live test.
Also another trick to check the water valve,
is to first cut the water off and remove the hoses off the back of the washer. Then one at a time point the hoses inside the washer tub and turn the water back on. If you don't have good water pressure, turn the water back off and remove the strainer that should be in one end of the hose. Inspect the strainer to see if it is stopped up, clean it and reinstall it. Now repeat this test. If you have good water pressure now, reinstall hose and your problem is fixed
By the way my advice is free cuz God is good!