You don't have to rebuild one as per say. grab a brand new head, realign the coil so its evenly spaced wraps and all nice, remove the silica wicks. Take a Qtip swab, twist it and thread through the bare coil, just till it begins to bunch up then back it off a ioda, trim, prime with juice, put it back together, few primer puffs and then take a vape. You'll amaze yourself.