ET4 Headlight problem

I wondered if anyone could help me?! I have a vespa et4 2002 and recently the headlight stopped working. Ive bought new bulbs and it still didnt work. The sidelight comes on. The high beam panel light doesnt come on when switched on either. Every other light on the bike comes on apart from the headlight. Ive traced the wiring and think it could be a relay(?) Its a 5 pin small black box with the words TRW Sipea 2855 12v/30a on it. Do you know if this could be the problem and what it is???
Cheers [:)]