I would be a good idea to clean off the blue corrosion on the circuit board and seal it with a lacquer to prevent further corrosion.
I did. Replacement battery seemed to die quite quickly (it was probably several years old) but I put a new one in Friday morning, and have likely done 500 miles and several cold starts since and it’s been fine.
Conformal coat is the way to go, but unfortunately not available easily and cheaply. If you have a PCB/A manufacturer nearby they might give it a quick spray for a donation to the Xmas party fund. If you were closer I'd have been happy to do it at work for you, we do our own Conformal coat after inspection.
