http://www.koopor.com/files/User-Manual/KOOPOR-Plus-User-Manual.pdf
I will save you some searching. There is the user manual. Information about switching between power and TC mode is on pages 7 and 8, though I recommend you read the entire thing a couple times just so you can fully know your device.
Also, as @Chasperk said, it could be a bad coil or a bad o-ring somewhere. I have had one with a bad o-ring on the base. Didn't really cause any issue, but I am sure it has the potential to.
I will save you some searching. There is the user manual. Information about switching between power and TC mode is on pages 7 and 8, though I recommend you read the entire thing a couple times just so you can fully know your device.
Also, as @Chasperk said, it could be a bad coil or a bad o-ring somewhere. I have had one with a bad o-ring on the base. Didn't really cause any issue, but I am sure it has the potential to.