sometimes the headlight plugs are wired opposite what the ballasts input is. Since halogen headlight bulbs have no polarity, whoever assembled the harness just put the wires in without worrying about polarity.

Check the vehicle headlight connectors, find which is the power and which is the ground. Also keep in mind that the accord has ground switched headlights... meaning there is always power at the lights, the ground leads are switched on and off... so if you connect a relay to the power side of one headlight plug and the other side of the relay coil to ground, the relay will be on all the time.