A card or a slot?
Usually the cards themselves are completely unpowered....they receive everything through the PCMCIA interface when plugged into the slot.
The easiest way to confirm that a PC Card is working is to plug it into a laptop with a PCMCIA bay that is known to be fully working, ie has all the drivers loaded and can operate with existing cards. The laptop will give a double beep when the card is inserted, and is operational. PCMCIA cards are hot pluggable as well, so no need to confuse matters by booting up with it. You may or may not be prompted for drivers for the card.