Does PWN stand for Pulse Width Modulation? If so, then putting in a normal relay won't work as it'll be opening and closing a hundred times a minute. You'd have to use a solid state relay.

Alternatively, you could use this controller:
http://www.ultimateyota.com/index.php?option=com_smf&Itemid=26&topic=50.0

Steve
My Website ||Gettin' off 4wheel drive club member
'93 4Runner V6 4x4 auto tranny
If you have to ask about a SAS, you're not ready for it.