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?