The wiper motors on the roadster can corrode quite easily. When they do, the wipers will get slower and slower until they no longer work. You will need to replace the assembly. A new one can be bought from smart under the following part number:

Q001 1612 V004 0000 00 (RHD)

Pull off the caps covering the wiper arm fastenings.

Using a 13mm spanner remove the nut and washer on each arm.

Once you have both sides to this stage you will need a puller tool.

The arms are on a splined shaft and should pop off as you tighten the tool.

Remove the two bolts on the black trim which covers the wiper mechanism.

It is possible to remove the trim without any further disassembly, but it is much easier if the wings and bonnet are removed!

The trim will first need to slide towards the front of the car to release it from under the bottom of the windscreen, where it is secured by several clips.

Lift it up and over the wiper arm drives, and put it to one side.

Remove the old wiper motor assembly by removing the three retaining bolts, and unplug the single connector.

Install the new assembly and reverse the operation, ensuring that all bolts and clips are secured.

Finally replace the wiper arms, ensuring you have them at the correct resting position, and tighten the retaining nut, not forgetting to replace the washer.