However, when I opened the motor to see if I was lucky enough it would just be a magnet on shaft repair, I found that the board had obvious signs of water damage. Unlike another poster on here, I was unable to desolder the board from the power connector to do any further repairs, so I ordered a motor from a breakers...
Now, as some of you might know, I am an engineer offshore, on oilrigs and boats, what very few of you will know is out there we use a product called denso tape, which is basically a fabric bandage impregnated with a brown wax oil type of stuff, making it very water repellent. We use it to protect cable glands, hydraulic fittings, flanges and bolts, lips on junction electrical boxes, etc. It is not a marine industry exclusive product, it can be had from Toolstation for about eight quid a roll:
What I've done with it is applied it to the seam where the lid of the gearbox which the ecu is mounted to, joins the main body, as an additional barrier to water ingress:
I'd suggest others look at this seam, and apply some additional sealing there, whether it be denso tape, or a coating, or a smear of an adhesive, as the corner of the motor lid lies in the lowest point of the scuttle's drain path, so it will ALWAYS be wet. I strongly recommend this as it looks like wiper motors are a weak spot on these vehicles, and at £140 for a used motor, £360 for a new one, vs £8 preventative maintenance, it's a no-brainer to me.
