Thanks guys! What's the PT's code that needs to be entered into the Garmin? Can't figure out where to get it. Might as well try it, though I think problem is in unit not waking up for whatever reason. And yes, I did swap the battery for a new one...

P.S. I went ahead and bought a new G3 cap. I also spoke to Powertap support and it seem that if new head does not fix the problem, I'll have to send them the whole wheel for overhaul - rather expensive, so keeping my fingers crossed...