You can have full voltage into a device, yet the device won't work cuz there are just not enough electrons able to pass into thru or out of the device.
True.
Had it happen on a jeep I was working on for someone. One of the battery cables had just enough of a connection internally, but once the starter put the circuit under load, everything would got out and stay out until the cable cooled off. Jumper wires, jumper cables and a test light can find an issue like that better than a volt meter sometimes.