To confirm/clarify what I thought to be the case with the operation of it, the motor has 4 pins: ground, permanent live, fast and slow. The permanent live is there to put the wipers into their parked position when power is removed from the fast/slow connections, and it does this via the park switch within the motor. I assume that when the motor is operating normally, the current through the permanent live is being monitored, and its regular connection/disconnection by the park switch during each revolution of the motor is what keeps the system happy. When this switching does not occur, the power to the high/low is removed to protect the system.
On the motor itself, there are externally accessible pins that are connected directly to the pins in the main connector, albeit covered in rubber. I removed this rubber so that I could check that the connectivity between motor and connector was good (possible not the best idea for maintaining the longevity of the motor, but I was struggling!). On mine, the permanent live was not connected. Once fixed, all was well.
That's the short story. By the time I got to that point, I had pulled the motor apart and reassembled it, bypassed the connector at the other end of the motor loom, soldered the loom directly to the above mentioned external pins, all sort of things! Although everything worked once reassembled, the motor had no power and struggled to move the blades (I confirmed this by connecting the motor directly to the battery). So, I fitted another used motor and loom. Sorted
Thanks to Ozvtr for his help in this thread, much appreciated.
