The battery-powered WP-360 Water Flosser eventually slows down, so I buy
another and set the old one aside to fix later. Today is later, to avoid the
infection risk of a shopping trip and the cost of yet another new one. After
prying the ribbed ring out with a Swiss Army knife can opener they
disassemble easily with a small Phillips. Inside is two tabbed AA NiMH
cells, a DC motor and pump, all of which come apart by removing fairly large
screws, unlike the tiny ones on another of today's projects.

The on-line repair suggestions are about replacing the battery, but when I
took apart an old one for practice the batteries were still charged and the
motor had corroded and seized solid. The current, slow one worked fine after
I had opened it, which is typical for me. Maybe a bit of clogging dirt was
dislodged? I see the same thing with small engine carburetors.

Electrically the 3.17VAC input float-charges the NiMh cells through a series
diode. The motor on my good one draws about 1 Amp from a metered power
supply, disassembled on the bench without the pump load. The battery voltage
dropped from 2.8V (external test charge) to 2.2V before disassembly, 2.5V
after.

The motor pinion drives a crown gear with an eccentric for the pump piston.
The eccentric might have a trace of factory grease on it. I oiled everything
that moves with "safe for plastics" light oil since I didn't find a
different suggestion.

Has anyone else fixed one of these with good/bad results?