This morning, I got bike out for the morning commute, and was wheeling it along my path when I noticed the back light wasn't working.
"Oh, dearie me" I said, or something like that anyway.
From experience hub dynamo systems work great, to the extent you forget they are there, up until the moment they don't, whereupon they are a right pain in the Saddle Interface Zone.
There are so many points in the system where things can go wrong completely at random.
Also, if I understood electricity I wouldn't have become a carpenter.
So I grabbed the backup bike ("Why do you have at least two bikes at any given moment?" people ask, well now you know...) and bombed off to work.
On my return I rather half-heartedly started pulling plugs out of the back light to see if I could find anything, scraping the dirt off them, crimping the contacts and and putting them back. Turned front wheel.
Not a sausage.
Looked at front, repeated the procedure. Turned wheel.
Burst of red shines on living room wall light like a rather low budget disco. Nearly drop bike in shock.
Roll bike back to parking space, light is still working.
Will keep checking it though, as I don't trust electronic things not to up and die on me if I don't keep an eye on them...