How accessible is the connector? If it is not too difficult, regular spraying with WD40 might help.

Vaseline was the traditional stuff for battery terminals.

That connector seems to be unfit for purpose. There are ones which look a bit like an accordion which are, presumably, waterproof.

(Does it rain in Dakar?)

Very limited access, in fact you can't really see the connector block and you certainly can't see into the module receiver block as it's facing the firewall just tucked under a steel shelf below the windscreen. The whole motor assembly has to be stripped out to really get at it.  And yes, In my opinion, it's not fit for purpose.  Sorry to be critical but it has the potential to have windscreen wiper and windscreen washers failure while driving.  Ford know this.  That may be ok at slow speeds and were you can pull over but not so good in heavy rain on the motorway.  Ford has advised me it's a known fault but not as yet a recall item.  The failure of the unit usually stops both the windscreen wipers and windscreen washers, both an MOT test item. 

The Dakar hasn't been to "Dakar" for many years and has been moving around, South America for a while and Saudi this year.  I think the worse instance was 2015 heavy rain in Bolivia on the salt flat stage.  The rain turned the salt into brine and instantaly attacked the softer metals.  The liquid acted like an electrolyte and sent power throughout the electrical system lighting them up like a christmas tree.  Even the factory teams had retirements that day.  I've rebuilt a ralley bike that was airlifted out from that stage.  It was toast. Couldn't believe the damage in such a short space of time.  

Very limited access, in fact you can't really see the connector block and you certainly can't see into the module receiver block as it's facing the firewall just tucked under a steel shelf below the windscreen. The whole motor assembly has to be stripped out to really get at it.  And yes, In my opinion, it's not fit for purpose.  Sorry to be critical but it has the potential to have windscreen wiper and windscreen washers failure while driving.  Ford know this.  That may be ok at slow speeds and were you can pull over but not so good in heavy rain on the motorway.  Ford has advised me it's a known fault but not as yet a recall item.  The failure of the unit usually stops both the windscreen wipers and windscreen washers, both an MOT test item. 

The Dakar hasn't been to "Dakar" for many years and has been moving around, South America for a while and Saudi this year.  I think the worse instance was 2015 heavy rain in Bolivia on the salt flat stage.  The rain turned the salt into brine and instantaly attacked the softer metals.  The liquid acted like an electrolyte and sent power throughout the electrical system lighting them up like a christmas tree.  Even the factory teams had retirements that day.  I've rebuilt a ralley bike that was airlifted out from that stage.  It was toast. Couldn't believe the damage in such a short space of time.