will drain but wont spin

I just had exactly the same problem. It turns out that the washer thought it was "continuously out of balance" because the inertial unbalance switch was not working properly. The way I fixed it was:

1. I followed the instructions to disassemble the Neptune washer found here: http://www.neptunehelp.com/index_files/Page323.htm and then in the control panel on top I found actually a very useful document stored in the control panel itself. It is called "Schematic Mini-manual LED Washer" and it contains a set of schematics for the electrical system and an explanation on how to run various diagnostics on the washer. This was incredibly helpful.

2. I checked the diagnostic code using the following procedure:

a. Plug the washer in for power.
b. Put the washer into "Service Mode" by holding the "Delicates" and "Heavy soil" keys simultaneously for 3 or more seconds. My washer showed a "00" on the screen when it was in Service Mode.
c. Pushed "Presoak" to put it in diagnostic code mode.
d. Pushed the down arrow key to read out the last diagnostic code. In my case the most recent diagnostic code was a "05", which the mini-manual says means "Continuous unbalanced circuit". In fact the mini-manual also says to "Check for: Faulty unbalance switches, Loose wire connections, Bad control board".
e. To find out how many cycles ago this happened, you can push the "Cotton/sturdy" button and it will tell you how many cycles ago this happened. I can't remember the response of my washer, but it either showed a "00" or "01".

To double check the diagnostic code, I

a. Cleared the list of diagnostic codes by holding the "Heavy soil" and "Presoak" buttons for 3 seconds while in the "Diagnostic code" mode;
b. Put the washer door back on and screwed it in without putting the entire front back on the washer.
c. Pushed the "off" button or unplug the washer and plug it back in to get it out of "Service mode".
c. Ran just the spin cycle, where it counted down to 7 and then was perfectly silent and then displayed a "00" without really trying to spin.

Double checking the diagnostic code probably wasnt' really needed, but I thought I would try it just to make sure. I did receive the "05" diagnostic code again.

3. With the washer unplugged again, I did the following to check that the switches were the problem, I checked the resistance of the circuit that has the following three switches in it: the inertial unbalance switch, the low tub displacement switch, and the upper tub displacement switch. If the circuit has effectively "0" Ohms of resistance, the switches are good. If you effectively have "infinite" resistance, then one of the switches is bad.

The mini-manual shows you where the switches are physically on the washer. The easiest way to check this is to find a connector that connects the three switches to the control panel. I found this by lifting the top panel of the washer up all of the way so I could access the top of the washer's tub. Based on the schematic from the mini-manual, the in-line connector has four wires. One side you will find a red wire with the number "23" on it and an orange wire with the number "40" on it. The other half of the connector has two blue wires connected to it, one with the number "23" on it and one with the number "40" on it. In my washer, this connector was placed on top of the washer toward the back.

To test to see if one of the switches is not working:
a. Disconnect the inline connector described above.
b. Test the resistance between the two terminals on the side of the connector having the two blue wires. I found that when I did this I had infinite resistance, so want of the switches was stuck open, indicating the "unbalanced " condition.

To find which switch was at fault, I disconnected each switch from the circuit and tested each one individually. The one that was easiest to get to was the lower tub displacement switch, which is in the front on the bottom of the washer's tub. It worked fine (0 Ohms resistance normally and infinite resistance when you push the button). The next I tried was the inertial unbalance switch, which is placed on the top, right, front of the tub just underneath the block of concrete that is mounted on the tub. For convenience, I removed the concrete block so I could easily access and remove the switch.

This was the switch with the problem (it was effectively stuck open or infinite resistance). It seems to have some rod of metal in it that moves back and forth with the washers motion, so I just shook it vigorously and you could hear the rod of metal move back and forth. This seemed to free up the switch mechanism and the switch functioned again (showed "0" ohms when it was held in about the same position as it would be on the washer). I put the switch back in place and checked the connector with the blue wires leading to all three switches as before. This time I received effectively "0" Ohms, meaning that the problem was fixed.

4. At this point, I put everything back together again (concrete block, reconnected the in-line connector to the switches, and reversed the procedure found in http://www.neptunehelp.com/index_files/Page323.htm ).

Once everything was back together again, I tested just a "spin" cycle and everything worked. You could also test this before putting things back together (probably a good idea) by temporarily putting the door on properly and trying a "spin" cycle.

Another thing to note, you could actually check the diagnostic codes and run several of the tests without taking the entire washer apart. Basically, all you need to do is get the mini-manual out of the control panel (I there are 6 screws total I took off) and run the tests before opening the rest of the washer.

In the end, it might be good to clean or lubricate the inertial unbalance switch or replace it since it will probably stick again. Unfortunately, I am not sure how it is built, so I am not sure what the best way to clean or lubricate it is. Just shaking it for the moment did the trick.

Hope this helps.