Just thinking out loud and would yield to someone with greater knowledge. Sometimes I've seen devices with 12V plugs have something inside that steps down the voltage.
So its remotely possible (again someone who knows more, please set the record straight) that you may have sent 12V to a device requiring much less and have damaged it.
(Yeah it was from personal experience. Ever since that, if I needed to lengthen a power wire, I went to the auto store and got the cigarette lighter extension cable and cut it to the appropriate length).
As noted above you get a solid red LED indicator on the puck when the right power is applied to it. When it locks in on GPS signals, it begins to blink red.