I have a Keurig K155 that I use at my office and have been using it without fail for almost three years now.
Lately, it keeps telling me to fill the water reservoir even though it is not empty. Sometimes re-seating the unit will work, but it can take several times.
I'm not sure what method the machine uses to detect water levels, nothing in the owner's manual or cleaning/maintenance manual seems to cover this problem.
There does appear to be a small hole where it does seem that there's a glass recessed where I'm thinking there might be an "electric eye" but I can see no other visible way for it to detect water level. I realize that's not likely it because the graphic display will show actual level, not just empty.
The manual does refer to a "float" device, but it doesn't document it very well, and it looks like it might be difficult to get to, requiring disassembly of the machine.
I have to admit (embarrassingly) that I've never cleaned the machine in the years we've all used it. Should that be my first step? equal parts white vinegar and water? Or is that likely to have no effect on my water level detection problem?