I just purchased a new MPPT 100/30 Charge Controller. Everything is working fine. However, I would like to change the Bluetooth PIN. It is asking for the PUK Code. I read on this forum that the PUK Code is on a label on the unit. The unit is already mounted, so I can see all sides except the back of the unit, which is primarily heat sink. However, I can find no label on the unit, or the box that says anything about a PUK Code. Where is the PUK Code???