54 plate a3 wipers not working

Just wondering if anyone can help I'm completely stuck, I have just bought a 54 plate a3 and the wipers don't work, there is power in the thick black/Brown wire obviously nothing in the brown one as it's earth(I'm guessing) also there's no power in the small purple wire, the guy I got it off said he put a new motor in it it worked for a week then stopped again can anyone help? I've tried unplugging the bonnet catch thing but that's not done anything, also on the dash it's saying auto wipers/auto lights malfunction