Martin says "They stop at whatever point they are on the windscreen when I
turn the switch off." and we have to believe him or call him, erm mistaken.
The parking arrangement from 1967 or so MGBs onwards is very different to
the earlier (and presumably MGA also) style. The plastic wiring connector
mounted on the wiper motor also contains the park switch. It has a plastic
peg that protrudes through the gearbox casing which rides on the large gear.
The connector/park switch is retained by a spring clip and can be removed by
sliding it away from the large gear spindle. Unfortunately it seems this
park switch is not available new, although one may be able to find a good
2nd-hand one. Incidentally mine broke internally recently and it resulted
in the wipers running continuously, I had to pull the arms off till I could
get home and have a look at it. The same would happen if the park
switch/connector assembly falls off the motor.
The park circuit goes through the manual wiper switch (you can find
schematics on the web site below, select 'Spanners', 'Electrics',
'Schematics' and 'Wipers' - yours should be 'Later two-speed') so if this
circuit is broken anywhere they will not park.
Either some mechanical aspect of the blades sticking caused the park switch
to become jammed, or its just coincidence.
PaulH.
----- Original Message -----
From: Bullwinkle <yd3@nvc.net>
To: Martin C. Jones <M.C.Jones@staffs.ac.uk>; mgs <mgs@autox.team.net>
Sent: Friday, January 12, 2001 7:43 AM
Subject: Re: Stupid Driver Wiper Problem
> Martin:
>
> I don't have a MGB book which covers the 1977 models but I have one
> which covers up to 1975. Also I don't have a MGB, but I have an MGA
> which is very similar in wiring to the MGB, so FWIW and please bear
> with me.
>
> I believe the problem is that the "park switch" is damaged. To better
> understand how the system works I will go through the early MGB motor
> first.
>
> On page N.15 of the manual I have is illustration N.13 which shows the
> internals of the wiper motor for an early MGB. Under the domed cover
> is a wiper contact (item 6) which slides over a copper segment inside
> the cover. The wiper motor opperates and parks as follows.
>
> 1) The wiper operates when one of two grounds wired in parallel is
> closed: One ground is the switch on the dash and the other is the
> wiper switch shown by item 6 in the diagram.
>
> 2) When the dash switch is shut off, the motor continues to operate as
> the sliding switch is making contact with the copper segment in side
> the cover.
>
> 3) When the sliding switch contact moves off the copper segment, both
> grounds are now open and the motor stops.
>
> On page N.32 of my manual is a two speed wiper motor for a 1975 MGB.
> At the bottom of the gear box is a device called the limit switch
> assembly. Most likely this switch senses the position of the large
> driving gear and would open and close contacts inside the motor just
> like the wiper type of the early motor. My guess is that a stud on
> the switch which may ride in a groove on the bottom or over a hump on
> the large gear is broken, bent, or out of place.
>
> Blake
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