My old 4/4 didn't have a relay Keith. When I rewired (with more suitable gauge wire) I also fitted a relay (and fuse!). I'd recommend you do so - but there may be one already fitted...?
Cheers,
Graham (G4FUJ)
Sold L44FOR 4/4 Giallo Fly '11 MINI Countryman Cooper D All4 '90 LR 90 SW