As the title says, I just got a Wii U second hand, only to realise it didn't come with the Gamepad charging cable. After having got one off Amazon, it's been sitting on charge with various games downloading for like 3 hours.

I finally go to use the console properly after Pokken Tournament finishes, go to tweak the brightness of the Gamepad and it starts flickering - like the charge icon is flickering back and forth as though the cable isn't connected, but it's only when the brightness is set to 5. I knock it back to 4 and keep going, then inside Pokken, everything's cool until I get to a stage select screen, at which point it gets all flickery again.

Removing the cable makes the battery light go red as if it's not done any charging in all this time, and putting it back in has the screen go from normal to dim and back again, with the light flashing orange in unison. The console hasn't been used for about 2 years from what I've been told, and as a total Wii U newbie, how do I go about troubleshooting this please?

Is it the cable, the gamepad, the Wii U USB connection? I'm pretty stumped, as googling is taking me into a few variations on this same thing, but with no specific cause (plus I trust you guys way more than a random thread on GFAQs)

Thanks!