The consecration icon will glow when you have 3 seconds left. After the 3 seconds the glow will disappear. This is to remind you to keep the consecration up. When you use consecration the icon will show. If you leave the area and no longer get the buff; the icon will disappear. When you reenter it will appear.
Consecration Renew Glow (icon)
Consecration 3 (icon)