There seems to be a corrosion problem in the relay box.My fan didn't work,might not have worked for some time,and examination showed the main positive lead that goes into lower female relay plug had corroded and broken.Saw one on ebay,when I got it it had exactly the same problem.So not wishing to take out a mortgage for a new loom I bodged it as follows.Take out the bottom relay,clean the pins while your at it,and open up the relay.Solder a cable of similar thickness to original to the copper relay frame.Drill a hole in the top of the relay and thread wire through.Close up relay.Clean up the other end of the corroded lead and crimp it to the end of the wire you have just soldered.Put everything back together.
Just done it.Fan works.