408 wipers: do they self park?

[PEU186F]

Yes, they should, given the original motor and switch. The system was dreamt up by a brilliantly contorted mind and relies on a certain amount of slack in the armature that drives the crank which in turn operates the wiper cables. When the armature rotates one way the crank operates the wipers in their normal arc, when rotated in reverse the wipers reverse and due to the deliberate slack in the armature operate in a different arc which then allows the cut off switch in the motor to come into play and stop the motor in the wiper park position.

The switch is a gloriously complicated thing in order to achieve off/park - slow - fast operation as it has to reverse the polarity of the feed to the motor between slow and park/off.

A further point which I think I’m right in saying is that power is fed from the motor to the switch and back again rather than to the switch and then to the motor.

This was all a bit to much for Bristols and you won’t find a Bristol wiring diagram that makes anything clear, but the good news is that these wiper mechanisms were used on other cars and the RR club of Australia have copies of the extremely detailed and well written RR technical manuals on their website. I have a faint recollection that I derived a wiring diagram a few years ago and I’ll endeavour to find it later today.

Note that the switch does NOT cut off power to the motor when it is returned to the park/off position, that is achieved by the cut off switch in the motor itself.

Probably not much help but I trust this may get you on the right track

Roger