How old is the bike?
You may have to take the non drive side cover off and clean all the crap and water out.
After you have done this unplug the cable going into the motor as moisture gets in there too and corrodes the contacts.
Dry everything as much as possible, if you have a compressor and an air hose it makes this task a lot easier. If you haven’t, then lots of paper towels (although these should be saved for wiping your arse due to the global shortage of toilet paper..... however, this is obviously an essential high priority job

)
Remove the battery out of the TCU before you put it on the radiator. Removing the battery can be a really fiddly task to do. I find a knocking motion on a semi soft surface pops it out.
Make sure you take note of the orientation of the TCU battery as you remove it as it not 100% obvious. Again, if you have an air hose you can blast the water out of the TCU. I would still put it on the radiator afterwards though.
For me and the conditions I ride in tape does not work for me, it unfortunately still get in. If you don’t live in a very wet climate you will probably be fine using tape. Horses for courses