Karcher WV Classic Window Cleaner: Motor Clearance, Rust, Charging Issues & Troubleshooting Steps

I have a problem with the Karcher WV Classic. After dismantling it turned out that the motor has a very large clearance on the sleeve, it is covered with a rust coating and on the electronics board there are white deposits or signs of rust in several places. I replaced the sleeves in the motor, cleaned the plate and corrected February.

Washer can be turned on, the motor works but there is still a problem with charging - after connecting the power supply (gives 5.2V) the battery starts charging for several seconds, the red light blinks and then turns on and the end of charging.

After several attempts I managed to recharge the AKU from 2.8 to 3.3V, but now after connecting the PSU, the continuous light is on and the charge is not charging. Where to start checking? Maybe someone had a similar problem because judging from other entries on the electrode, karcher did not show off this product ...
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I had a similar case and used a separate battery charging system in my case (LTH7).

For me, however, it helped to clean the tile thoroughly, improving all soldered solders.