do you mean you can't find it or that you've found lots of relays and don't know which one? dont know fiesta's but have you tried under the bonnet? Once you think you've found it put wipers on second setting and listen for the 'click' from the relevant relay, it'll do this every time wiper starts and means this function IS working, now try first setting and if theres no click you'll need a new relay! relays are mechanical (and timers) as well as electrical. You don't need the engine running as you may not hear the all important 'click'. good luck.
Chris P.Duck, February 2010