Unplug it, leave cover open, place it to a hot corner under sun light and wait like 5~7 days... then try again. If not, repeat the process until it dries complety...

The unit is easy to dismantle, with the screws underneath (some of which are hidden under the runners). But you need to be very careful, as the electronic circuit is not insulated and it is very easy to electrocute yourself once the device is open. Even when disconnected, the capacitors hold a residual charge.

Then dry it with hot air, e.g. a hairdryer.