Rick Morrison wrote:
>
> Sorry Paul, gotta disagree with you.
> All the MG wiper switches I've come across are of the "single pole,
> single throw" variety.
> When you cut the switch off, it's off.
> The parking switch in intergal with the wiper motor, and operates by
> recieving 12v power from another source (ususally the white circuit from
> the ignition switch). Then the power from the wiper switch is interupted,
> and the ignition is on, the wiper will continue to operate until the
> detent on the wiper gear opens the contact in the parking switch,
> stopping the motor.
The Leyland Workshop Manual shows 62-67 cars with single speed wipers
having 12v at the motor (green, not white) and being operated by a
ground from the switch - indeed a single pole single throw and just two
wires. After that a more complicated arrangement was in force where the
12v to operate the wipers came from the switch, but the 12v to park was
still on the motor. When the switch was in the 'off' position it 'made'
the park circuit. The park circuit was broken when the wipers were on
because, instead of the park switch simply disconnecting 12v from the
winding, it connected ground to it instead. This technique results in
the motor stopping much more quickly and the blades being parked in a
more consistent position. If the park circuit was still connected while
the wipers were switched on the park switch would connect ground to 12v
each time the blades passed their parked position. These later switches
have four wires and the motors five (not counting the ground
connection).
PaulH.
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