So here is what I and everyone else missed: I forgot about the vented loop! This is a failure of the vented loop. My big summer trip starts this Saturday and will be working to access the vented loop and see if it needs replacing or if one of the wires fell off. There are a couple of good boatyards along the trip. Anyone know what the part number is for the vented loop? And the access to the loop is "almost" impossible, but it can be done. About 25 years ago the hose fell off of the pump out deck plate (Peggy was involved with that nightmare) and I had to get to the underside to put it back on. My memory is the vented loop is there too. You take out the wood in the cabinet at the forward end and then move the AC hose. The toilet works fine for No. 1, by pouring a bowl of fresh water in, but there will be no No. 2 until further notice.