I hope you have not got the same problem that i had. Mine was the wiper motor in the end. My car is a iv as well and when i got it last year it was not long befor my wipers went funny. First off they would not work in one mode then the other then they went slow all together. I was stuck in cornwall at the time and had to get back to ireland in april. all i could do was get a motor from a scrappy that had the same mountings as mine and wire it direct to the battery with 2 wires in the front of the car for the g/f to touch together every time it rained.
If it is your wipper motor ask [email protected] ,that was where igot mine and fitted it my self so no to bad of a job to do.
hope this helps