Windscreen Wiper return?

I`ve got a 1991 H reg, 200TDI Series 1 Discovery manual, which when the wipers are work, operate fine, but when trying to switch them off or park them(what ever the expression is) they stop in the postion where you switch them off and don`t ride down to the bottom of the windscreen, like other cars do, i`ve read in the small history the vehicle came with and it mention something about a windcreen sender unit(??), can this thing be quickly remedied or is it something that a more experienced person should attempt at?

If it's the same as a 90 then I'll bet a pound to a pinch of **** that the electrical connectors are corroded on the drive motor connector block. It's easy enough to clean them up, on a 90 anyway.

I drove around for a couple of years with exactly this problem believing it was a tricky electrical fault until I could stand it no more. On investigation I found it was the wiper linkage: one of them was seized ALMOST solid at the point the wiper arm swings on. Follow the Haynes manual to remove the entire motor/linkage assembly. It is much easier than it sound's as it's quite small. With the assembly out you can work the seized part with oil/molegrips and a tiny bit of heat. Don't go in heavy-handed. It cost nothing to fix except a couple of hours.