Wiring for series 1 wiper motor

I am completely flummoxed by the wiring for this motor. Here’s what i have done so far
Completely rebuilt the motor and bench tested it works fine including that the eccentric cam does as it should and the rack moves further in reverse than it does forward. The limit switch checked and works as it should.
Put it into the car and it runs beautifully at both speeds but wont self park…
I read that when switched from slow speed to stop the dash switch reverses the voltage so should make pin 1 on the motor 12v positive, which it does, and pin 5 negative, which it doesn’t, hence it doesn’t reverse and the self park system doesn’t.
Ok now it gets fun, my question is how does this motor get its earth in any position? I cant find an earth return in the wiring diagram. I am using diagram W54955069 in the Jaguar service manual. I have cleaned and tested the dash switch, it works fine, I have the following connections in the switch.
Off pins 5 to7 and 6 to 8
Slow speed 3 to 5 and 4 to 6
High speed 1 to 3 and 2 to 4

It runs in both speeds thus at first sight since to run pin one on the motor needs to be earthed, it looks like the white/ light green on pin 1 gets an earth via the black wire on pin 4 in the plug which in turn connects internally within the limit switch to pin 2 the brown/light green but it in turn only goes to pin 8 on the dash switch and nowhere else. What am I missing? the drawing of the whole switch system shown no earth return that I can find. Is there something missing on the drawing?

Any help appreciated

Ian

Since you are well into it; I can just give you some food for thought, Ian…

In ‘high’ and ‘low’ speeds the ‘park’ switch is bypassed - power and ground is made at the stalk switch. The ‘high’ and ‘low’ motor brush is powered - the ‘third’ brush is grounded in the stalk switch.

In ‘off’; power is delivered from the stalk switch to the ‘third’ switch. Ground is provided by the park switch (to the ‘low/high’(?) brush). until wipers reaches the parked position - motor direction reversed. At parking, the park switch switches (from ground to the previously grounded ‘low/high’ brush) - applying the stalk power to that brush. With both brushes at 12V - the motor stops.

As an aside; if the excentric cam in the park switching was misplaced during rebuild, or malfunctions; the self parking will fail.

Frank
xj6 85 Sov Europe (UK/NZ)

Here is the Lucas wiper motor wiring schematicLucas16.pdf (255.6 KB) I have found helpful.

Thanks Roger that is exactly what I needed and shows 4 black as being earthed. The manual circuit diagram does not show the earth on that wire. Mine wasn’t, now is and now self parks as it should, unfortuanately at present on the wrong side but that’s an easy fix.

Thanks again

Ian

1 Like

**
That means that the cam operating the parking switch is reversed, Ian. A month ago the RHD/LHD wiper parking conversion was presented…

Look up ‘LHD versus RHD wiper motor parking’ - problem and solution described…

Frank
xj6 85 Sov Europe (UK/NZ)
**

Hi Frank
That thread was mine, I am now back from Oz to Europe and put in the motor I bought in NZ. It is now working ok and I have changed the parking side. Now working well.
Thanks

Ian

I spent some considerable time wrapping some mind around the wiper parking wiring.
At first I found usable schematics for Triumph cars and based on that I figured things out.
Finally I opened up the XJ6 Series

Gunnar,

could it be some part of your last post got lost under way?:slight_smile:

For the original poster things may have come to an end. For those doing an archive search in the future the bits of info may come in handy:

The internal connections are illustrated in the SI ROM

The wiring scheme might depend on the year of the car. This is for early cars
grafik

and this for later cars

At first glance I couldn’t spot any changes to the wiper/washer circuits though.

Best

Jochen

75 XJ6L 4.2 auto (UK spec)

Indeed my post here got partially lost. But I wrote a comprehensive story of my findings as a PDF,
will see if I find it.

I found the same circuit schematic you show.
and I enhanced it a bit to illustrate the three states of the dash wiper switch position.
This can help to follow the logic for those who do not in their mind easily convert
number pairs to circuit wires.
Green color shows what connections the switch will bridge in its three states.

Still fairly complex to wrap ones mind around. I will see if I find the long essay I wrote about it.

There is a lot of stuff going on there as the wiper motor comes to the park position.

The dash switch moving to OFF position from NORMAL is the most complex event
since during motor operation this sets in motion a set of events to park the wipers.
When that happens the motor is running at NORMAL speed.

(1) Turning dash switch to off position inverts polarity to the wiper motor (!) so the wiper arms do a little extra twitch dance over the windscreen before coming to rest.

(2) As soon as the park switch (named “Limit switch” in diagram) then closes, motor windings are short circuited to accomplish instant braking of the motor !

Not all evident at once just by a casual glance at the circuit.

One of the most complex circuits engineers figured out during this automobile era.
Most common problem seems to be the park switch on the wiper motor (if wipers find some use) with time ceases to work properly since over its lifetime it mechanically opens and closes for each wiper stroke across the screen. So some wear occurs.
In my case I was able to cut open the plastic enclosure of the motor park switch, adjust it so it worked and glued the enclosure back in shape. Seems the company Limora still sell this switch as a spare.

See the three dash wiper switch positions :



1 Like

Not ‘shorted’ Gunnar - 12V is applied to ‘both’ motor connections, and the motor ‘forcibly’ stops…

Frank
xj6 85 Sov Europe (UK/NZ)

If you apply 12V to both connections nothing happens. But if you apply two 12V leads from the same source (battery post etc) the motor is simply shorted and that is why it stops quickly. Same thing with the window motors. The permanent magnet motors stop because when turned they act as a generator and being shorted they are working against the wiring.

The park switch just changes one of the brushes from ‘ground’ to 12V, David - the other one stays at`12V. I would not use ‘short’, in electric parlance, for that…?

Frank
xj6 85 Sov Europe (UK/NZ)

If both wires are switched to 12V from the same source, they are shorted!

If you connect 12V from the same source to the two poles of a electric motor nothing happens, the voltage differential is zero.
What happens though is that when you try to spin the motor it creates a magnetic field that opposes the direction of the motor.
Common practice on electric fans so they don’t spin, and wear, for no reason.

Precisely, they are shorted not from the battery perspective but the motor (now a generator) sees a short circuit.

1 Like