A puff of smoke but still seems to be working
 

My woeful soldering seems to have caused a puff of smoke from my Speedo. Think it was because of solder touching between terminals on the motor

Sorted that and the Speedo seems fine. Surely a puff of smoke if bad but if it is how can it still be working?

Bottom line is that a puff of smoke means something has blown. If it’s still working I would say it’s a capacitor or a transistor but ultimately something has gone.