A Quick Word About.....The Mysteries Of The DS Wiper Motor.

Over the years I've seen lots of posts on Facebook and other forums about problems with DS wiper motors. Posts like this....

And this...... 

And this.....

This one (drawing power with motor off):

And how about this?

These examples relate to 1968 cars that have the same wiper motor, and wiper motor switch as my car. Heat seems to be a theme. Heat is bad. Especially if the motor is meant to be turned off because heat can cause a fire..... The other theme seems to be confusion over how to wire the wiper motor up - what connections go where. And why. 

 

A wiring/ colour coding problem I discovered when I rebult my wiper motor reminded me of these other problems and I decided to get to the bottom of my wiper motor circuitry once and for all.

Just to be clear, this is about a Bosch wiper motor from a mid/ late 1960s car, controlled by a knob on the dashboard. I don't know how much of this will be relevant to later cars (October 1969 onwards) that have the wipers controlled by a stalk on the dash. The two unit's are easy to distinguish. Later  - post October 1969 - cars have FOUR cables and solder points on the gear head.

Later four wire motor (photo credit: Mathieu Dutre)

My car, with a two-speed mechanism has THREE contact points and solder terminals.

Two speed motor with three solder points

 Cars from the early 60s had one speed motors with just TWO contact points.

One speed motor with two solder points (photo by PaulE)

These earlier one speed wipers were controlled by a simple 'pull/ push', 'on/ off' knob.

Pull/ push wiper switch for one speed wipers

When the two speed wipers (like mine) were introduced, the knob looked similar, but rotated between 'off' slow' and 'fast'. The head of the knob has an arrow on it so you can tell what speed position its in. This photo shows 'off'.

Twisting switch for two speed wipers - note arrow

I recently dismantled and rebuilt my wiper motor and studied how it was wired. You can read about that HERE. I'm going to walk through all the components and connections. Then I'm going to propose  some wiring diagrams showing how the circuits fit together. Then  - based on that - I'm going to describe how it seems to work.

Power supply to the Switch and Wiper Motor

From the battery, the 12V supply goes into the loom and emerges at a fuse (the yellow colour-coded fuse)  - which just happens to be over by the wiper motor.

Fuse box under the wiper motor

From there, the supply goes back into the loom and splits into two feeds.  Once feed goes to the wiper switch on the dashboard.

 

It's worth pointing out that there is another similar arrow-headed switch on the dashboard - the switch for the parking lights (off, right and left). If you are groping around with wiring behind a part-dismantled dash, it's easy to get these muddled. The wiper motor switch has THREE pins on the back.

Wiper switch has THREE pins

The power from the loom connects to the green colour coded terminal of the wiper switch. That is power 'in' to the switch.

'Green' is power in to the switch

The other two terminals (red and blue) are power out of the switch.

'Red' and 'blue' are power from the switch to the wiper motor

The wires that connect to red and blue go back in to the loom and emerge in the engine bay at the motor and still have red and blue tags. The other branch of supply from the fuse goes directly to the wiper motor area as the black tagged contact.

The three wiper motor connections coming from the loom

All three of these wires are for carrying supply to the wiper motor. Remember that the black-tagged supply does not pass through the wiper switch or the cars ignition switch. Other than the fuse blowing - It's permanently live.

 

So what you find coming from your loom at your wiper motor is:

• a black tagged wire (permanent live feed)
• a blue tagged wire (switched feed from the dashboard switch)
• a red tagged wire (switched feed from the dashboard switch)
  

External wiper motor connections

On the alloy gear housing of the motor is a cream or off white platic insulating strip with three solder connections points. The alloy gear housing also has an 'eye' hole through which these three wires pass. It's just a cable tidy really but serves as a useful reference point. I'm going to call the solder point furthest from the eye 'solder point A'. I'm going to call the middle solder point 'solder point B' and the solder point nearest to the eye..............'solder point C'.

 

Arbitrary labelling of the solder points

Each of these solder points has a short colour-coded wire with a male bullet connector on it.

These connect to the three equivalent coloured wires on coming out of the loom.

Three power supplies to the wiper motor

Two wires emerge from a hole in the gear housing near where it joins the main motor body.

There is a thick wire in a brown woven sleeve. This also joins to solder point B - the middle solder point.

Note that the brown sleeved wire is a thick wire

The other wire is a thin wire in a white plastic sleeve. This joins to soder point A - the one furthest from the eye hole.

Note that the white sleeved wire is a thin wire

 

Inside the Gear Casing

With the motor taken apart we can see what is going on on the other side of that cream plastic insulating strip. Solder points 'B' and 'C' have two contacts that extend into the casing body. The end of solder point 'A' is just bent over to secure it within the cream plastic strip.

The wiper motor gear wheel is within the gear casing lid. It's made of nylon or some similar material, but has a conductive metal disc on it's surface. When the gear casing lid is fitted, the two contacts described above both contact the metal disk as the gear wheel rotates. Note that the disc has a segment cut out around it's outer circumference.

 

Wiper Motor Body - Internal connections

I'm now going to follow the two wires from the outside of the cream plastic insulating strip back into the motor itself.

The thick wire in the brown woven sleeve is one end of a 'stator' winding fixed to the inside of the motor body.

 

The thin wire in the white plastic sleeve also goes to the same 'stator' winding core (arrowed) - fixed to the inside of the motor body. 

The two wires are wound around the same core

Crucially, and although this winding is part of the same overall winding as that of the thick wire  - the two are insulated from each other. 

 

In this next photo of the other end of the motor body, you can clearly see how these two (thick and thin) wires come from the same core.

The other end of the thick wire goes to one of the armature brushes at the other end of the motor body. I'm going to call this 'brush 1'.

The other end of the thin wire goes to the other brush. Yep:  'brush 2'.

As you might expect for a motor, there is another stator winding opposite the one(s) just described above. This is made of thick wire. At the gear casing end of the motor body, one bare end of the wire is fixed to the steel casing somehow - possibly soldered?

One end is fixed to the casing

The other end of this winding joins 'brush 2' along with the thin wire.

That's just about it: all the wires and their end points are accounted-for. Having described the connectons on the motor brushes, I'm not going to bother describing the armature - the part that turns - as it can't really be fitted or connected wrongly.

 

So what's going on? How does the wiper motor actually work?

Circuit Diagram(s)

This is the diagram for a mid/ late 1960s two speed wiper motor found in the repair manuals. The Citroen workshop manuals show how the motors are wired into the cars loom, but don't show the detail of connections inside the switch and wiring inside ther wiper motor.

Note  connections 'Bl10' and 'R11' on the wiper switch (30)

 In fact even what the manuals do show can include errors with colour coding...

Incorrect: note how 'R11' at the wiper switch (42) has become 'Bl11'........

There is a variant diagram as, for a few short months Citroen briefly fitted an additional flying earth lead to the outside of the casing but in all other respects the circuits are the same.

Short-lived additional flying earth lead (49)

Someone also posted another snippet of a circuit diagram relevant to 1967/68 wiper motors, but I don't where it originated.

These kinds of diagrams are helpful for showing connections of the loom, but don't explain how/ why the wiper motor works. To me, the most useful thing about the diagram above is that it shows that it's the 'Bl' (blue) wire that is part of the 'park' mechanism - rather than the 'R' (red) wire. That narrows it down a bit!

 

Based on my photos and the wiring described above, I produced my own circuit diagrams and I'll tell you how I think it operates. I'm not an auto-electrician and these diagrams are intended to show the 'active circuits' - the circuits doing the work in the given scenarios. I have greyed-out wires and connections not playing a key role. the diagrams are about current flow - and so motor operation - though this is not to say that electical testing will not show continuity between some points.

 

Basic Wiring Diagram

This is the 'basic' diagram that shows all of the wiring.

Note how the thick wire coil coming from solder point 'B' goes from 'Brush 1' and through the armature to reach 'Brush 2' and the second, thick-wound coil. Note how the thin wire coil bypasses 'Brush 1'.

 

Slow speed - first knob position
In 'slow' mode, the contacts inside the switch provide power to both the red and blue contacts and so both the red and blue inputs to the wiper motor. Power goes into the motor directly via the wires connected to the solder points (points 'A' and 'B'). The sweeper brushes on the gear inside the gear case play no role.

In this switch position power flows through the winding made of thicker wire and the winding made of thin wire. The circuit of the thin wire is earthed via 'Brush 2' and so links to the other, thick wire, stator winding and earth. As such, all the stator windings are activated. In bench tests, the current draw on a motor was about 4.4 amps.

Switch in 'slow' position: current draw was about 4.4 amps.

Fast Speed - Second Knob Position
In 'fast' mode, the contacts inside the switch only provide power to the blue contact of the switch, and so only to the blue input on the wiper motor. Power goes into the motor directly via the wire connected to the solder point 'B'. The sweeper brushes on the gear inside the gear case play no role.

 In this switch position there is no power to, and through, the stator winding made of thin wire. In bench tests the current draw on the motor reduced to about 3.0 amps. With the stator field reduced, the result is that the armature is able to turn faster.

Switch in 'fast' position - current draw is now only about 3.0 amps

The principle at play here is apparently called "field weakening". Here is something I stole from a Google search:

 

"Field weakening is a motor control technique that allows the motor to operate at speeds above its rated speed by weakening the magnetic field in the motor’s stator. By reducing the magnetic field strength, the back electromotive force (EMF) decreases, enabling the motor to rotate at higher speeds."

So there you are....

'Off' Position - During Parking of the Motor

If the wipers have been running, when the switch is put to the 'off' position, the wipers continue to run momentarily. Even though no current is flowing through the dash switch, the motor has an independent permanent supply via the black-tagged contact (solder point 'C'). 

During the 'parking' stage, the sweeper brushes inside the gear casing - and the metal plate on the gear wheel - play a crucial role. The permanent supply to the motor via solder point 'C' leads to a sweeper brush inside the gear casing (the one with the nipple in the photo below). The sweeper brush contacts the metal disc on the gear wheel as it rotates.

As well as there being a direct wire-to-wire contact between solder point 'B' and the first thick wire coil, solder point 'B' also has a sweeper arm that contacts the metal disc on the gear wheel as it rotates.

When the dash switch is initially put in the 'off position', the motor continues to turn because power is able to enter the motor via the brush under solder point 'C', travel through the disc on the gear wheel........

Note the cut out segment in the outer track

.......go back out of the motor via the sweeper brush on solder point 'B' and, from there pick up on the point 'B' circuit -  the thick wire circuit to the windings and armature.

Off Position - Motor 'Parked'

Although, with the switch in the 'off' position the motor initially runs on, this running of the motor - and so rotation of the gear wheel - ultimately cuts off the power supply to the motor. 

The outer circumference of the disc on the gear wheel has a segment cut out. When the rotation of the gear wheel is such that the brush under solder point 'C' is over the non-conducting segment of the metal disc, power is no longer able to flow through the disc and back up and out via the other sweeper attached under point 'B'.

Although there is a permanent power feed to point 'C' on the outside of the motor, it cannot access the circutry associated with point 'B' and so the motor stops turning.

When the wiper switch on the dashboard is next switched either the 'slow' or 'fast' speed positions, power flows directly through solder point 'B' (or points 'A' and 'B' together) and so bypasses the 'parked' metal disc. The motor is able to turn again.

PROBLEM SOLVING

So what might account for the symptoms described in the Facebook mesages at the beginning of this post? 

 

Wiper Motor Switch Only Works with The Ignition On

The supply from the battery goes directly to the fuse. From the fuse, one branch of the supply  goes directly to the motor and the other branch goes to the wiper switch on the dashboard. It doesn't first go through the ignition circuit. If the ignition is controlling the wiper switch, then the supply into the wiper switch must (wrongly) be coming from a 'switched' source - meaning incorrect wiring or the wrong wire connected behind the dash.

 

Motor Get Hot Even With The Switch In The Off Position

If the motor is getting hot, this implies there is current flowing through one of the windings. Any current going through solder point 'B' passes through both thick wire windings and the armature, so there would be motor rotation. It's basically the 'fast' mode setting.

Any current passing through solder point 'A'  but not solder points 'B' or 'C' would flow through the thin wire winding and the second thick wire winding before going to earth. Crucially it would not flow through the brushes and armature and so there is no motor movement. To me, this  false 'off' scenario has the potential to make the windings hot. 

If this heating up is occuring with the switch in the 'off' postion, then it implies that the supply causing the heat is bypassing the switch. This in turn implies that the black-tagged, permanently live feed coming from the loom at the motor has been connected to the short red-tagged wire connected to solder point 'A' at the motor, instead of the wire connected to solder point 'C'. Remember that in this scenario the thin, and one thick, winding are permanently connected to a power supply and earth. Like this:

A wiring error like this may account for a hot motor when 'off'

 

Motor Gets Hot When Switched Off, But Otherwise Works As Intended

I couldn't work this one out. if the heat (when off) is attributable to putting the intended solder point 'C' wire to solder point 'A', as above, and if the wiper switch is assumed to be wired up correctly, then the two wires from the switch can only go to solder points 'B' and 'C'.

As these two contacts ('B' and 'C') are connected through the park function, then putting the wiper switch in either 'slow' or 'fast' would indeed cause the wiper motor to operate. However I think the two speeds would be the same - both 'slow' - because the thin coil winding is permamently live?

 

Switch Works - But In The Opposite Direction

This one I really couldn't work out. The inference is that the expected 'fast' switch position actually equates to 'parked' and the 'parked' position equates to 'fast'. 

 

The wiper switch has one power feed to it and two sources of power coming out - depending on the switch position. In it's intended 'off' position, no current flows from the switch - so I can't see how this can equate to a fast wiper speed. 

Other Problems

There is a joker in the pack..... In this post I have described the middle solder point on the motor  (solder point 'B') as the one having a blue-tagged connection. Because of how the swiper switch works (and how the windings have to work together to produce 'slow' and 'fast' speeds), I feel that is correct. And it matches one of the workshop wiring diagrams earlier in this post.

However if you've read my previous post HERE - about my wiper motor rebuild - you will see that on my motor, and the spare one I obtained, the middle wire had the red tag. The blue tag was on the wire connected to solder point 'C'.

These coloured tags are in the wrong order...

Until my recent motor build, a lot of my thinking - and my contribution to discussions - was based on this (mis) understanding.....Ooops! But I'm not alone. here's another wired that same way:

Red tagged wire is in the middle position..... (photo credit Maac95)

Right. Enough excuses. If you correctly wire up your wiper switch, but follow this incorrect wiring at the motor (so blue to 'wrong blue', and red to 'wrong red'), what do you get? Well....in the 'slow wipe' position, the motor runs normally.

 

However iIn the 'fast wipe' switch position, the motor turns momentarily until the 'park' position is hit. It then stops but is still drawing a current - so will probably get hot..... 

I tested this theory. I incorrectly connected the motor to the switch as described. Slow speed worked, but not fast - although the motor continued to draw about 2 amps. I didn't wait to see if the motor got hot - but I'm sure it would have done. 

So how come  - if my tags are muddled - the motor on my car worked fine and had two speeds? Was there a manufacturing error somewhere at some time that Citroen addressed simply by swapping over connections behind the dash? It's possible, but now that my dash and original loom are out, I'll never know how it was wired when it was originally working.

 

It's an easy fix though: I simply swapped the tags on the wires over!

Windscreen Wiper Motor - Strip Down and Overhaul

A clean up of the wiper motor was much needed and gave me the chance to service it. I discovered a lot along the way and plan to write a seperate '"A Quick Word About..." post on how the wiper seems to work - so this is just about stripping, cleaning and rebuilding......(I've done that now -  can read about it HERE).

My wiper motor - refitted. Note that it has three solder points on the body

Just to be clear, this was a rebuild of a Bosch wiper motor from a mid/ late 1960s car, controlled by a knob on the dashboard.

Wiper switch on the dash (photo credit: Carl Kirk)

I don't know how much of this will be relevant to later cars (October 1969 onwards) that have the wipers controlled by a stalk on the dash. The two wiper units are easy to distinguish. Later  - post October 1968 - cars have FOUR cables and solder points on the gear casing. As per the photo above my car, with a two-speed mechanism, has THREE contact points and solder terminals.

 

I'd always anticipated dismantling and servicing the wiper motor - not least because the body and mounting brackets looked decidely tired and dirty and, if not tackled, would make my restored engine bay look shabby.......

A 'before' shot: everything looking shabby.

However the motor is held on by three bolts only accessible from behind the dash.

 

With the dashboard out (that's a WHOLE other job....) you can see the wiper linkage mechanism.

The wiper motor bolts and linkage are right behind the dashboard

Anyway, with my dash long removed and a host of other jobs tackled, it was finally time to clean up the wiper motor. The Citroen instructions for removing the wiper motor can be found at Operation D.560-1 in section 3 of volume 2 of manual 814.

 

Before you remove anything, you need to make sure your wiper motor is in the 'off' position. Not just the switch, but the motor and linkage itself - it's the position with the wiper arms 'parked' at the bottom of the windscreen.

Wiper park position for 'parallel' wipers

If your car is still all wired up, this might be as simple as operating ther wipers, and then turning them off - so they 'park'. However, my car was in pieces with no dash controls, battery - or loom for that matter - and so I needed to improvise. I actually did this with the motor still on the car of course, but the next few photos explain the principle of what I did. I connected the negative side of a 12V supply to the body of the wiper motor. I connected the positive side of the supply to the motor wire with a BLACK tag. 

Finding the 'park' position: earth and BLACK tagged wire

The wiper motor operated for a moment but then stopped. That's the 'park' position. If you do this and want to check a second time, do this: leave the negative connection on the motor body but move the power supply to the middle solder point. (in my case the wire tag was coloured red - but it's better that we just call it the middle wire). The motor should run continuously.

Continuous running: earth and MIDDLE wire

Now disconnect the supply and reconnect it to the wire with the black tag once again. As before, the motor should run for a moment but then stop. That should be the park point. 

 

With my motor in it's 'park' position, behind the dashboard I noted the angle of the motor connecting rod (the one on the motor shaft) relative to the wiper control arm on top of it. On a left hand drive car, it should look like this - with the control arm in line with, and over the top of, the motor connecting rod and approximately at a '4 o'clock' position.

Wiper linkage on the wiper motor arm

 I hope that makes sense. No? Okay, here's what Citroen say:

Chapter and verse...

I also noted the orientation of the triangular back clamp plate behind the dash. The top side has a little scallop scooped out if it helps. 

Note the orientation of the 'scallop'

There should be a small circlip on the tip of the wiper linkage join - where the control rod is connected to the motor connecting rod. However mine had alread fallen off somewhere behind my dash. Anyway, with that circlip removed, the control rod can be removed from the motor connecting rod. It's a nylon bush on a metal balljoint and pops off if you lever it with a screwdriver.  

 

Removing the three bolts from the back triangular clamp plate enabled me to remove the wiper motor - and triangular face plate - from the car from the engine bay side. Note the triangular rubber gasket. This is a water-tight seal to stop any stray engine bay water getting behind your dash. To get at the wiper motor itself needed to remove the front face plate. To do that, I needed to remove the motor connecting rod.

Do you remember I said that it was important to have the correct alignment between the motor connecting rod on the shaft and the control rod? Well, for reassembly, (and with the motor still in it's 'park' position) it's equally important to have the correct alignment between the connecting rod and the motor shaft it is bolted to - so while the motor is still together and in it's 'park' position, I put a small scratch across mine.

Note the scratch across the drive arm and shaft

Don't worry if you forget. As per the official Citroen instructions above, the motor connecting rod can be removed and realigned later if you really need to.

 

Removing the nut on the motor shaft enabled me to gently prise-off the motor connecting rod. It was pushed onto splines on the  shaft to stop it working loose and rotating independently. 

Shaft splines, face plate, and water-tight seal

As with the back traingular clamp plate, I noted the orientation of the front face plate relative to the wiper motor body - and also which side faced the motor and which the dash. Again, a scallop on one edge served as a reference point.

Note the scallop on the right hand edge in this photo

The orientation of this plate is important as the holes in the plate that screw it to the motor body are not eveny spaced around the triangle: if you fit the face plate the wrongway round, when you come to mount the motor to the dash you will find your motor points at the wrong angle. It may get in the way of your 'Transpar' screen wash bottle or may even stop the bonnet closing.

The face plate was reluctant to be removed. I found that it had become stuck to a  foam rubber seal around the shaft hole. With the three plate screws removed,. Some gentle leverage freed up the plate.

Foam seal under the triangular plate

Now...the wiper motor is earthed to the car's chassis through it's body. However from February 1968 - so partly into the 1968 model year - Citroen apparently fitted an extra 'flying' earth lead to the motor body......

Extra flying earth lead - labelled '49' in this diagram.....

From other clues, I'd estimated my car was built in spring or summer 1968 - at the very least, post February 1968. However the absence of that earth lead put a question mark over my estimate. But now the mystery was solved. My car had indeed had the extra earth lead.  However all that was left was the end of a brass ring connector under the head of one of the screws.

All that remains of the flying earth lead

It would have looked like this......

Flying earth lead - as it should be

As this brass ring fixture is tucked away behind the triangular face plate, I would have to remember to make a new earth lead when I put the motor back together and before I fitted it to the car.

 

When the lid of the gear casing was removed, the gear came away with it. It was hard to see what's going on inside the casing because of all the dark, thick, grease in there. In my case, I also found a strange loose strip of metal..... I wasn't really sure what it was - but it certainly wasn't meant to be loose and suspended in grease.

At some point in the past I'd acquired a spare wiper motor, thinking it would sit on a shelf until I had an emergency. It turned out I needed it sooner than I expected.

I started to dismantle this second motor along side mine. Dismantling a second motor enabled me to compare the two, confirm they were assembled in the same way and cement some learning.

Compare and contrast. Spot the difference......

And that it did. It soon became clear that the broken piece in mine was an electrical contact - one of two that should be there. 

There should be two electrical contacts inside the casing

Mine had snapped off at some point. 

The contact had snapped off

I'd not been heavy handed when I cleaned out the grease so I don't know how it came to be broken. Perhaps the motor had been run in reverse and it had snagged? I just counted myself lucky that I had a spare motor. Whatever the cause, the learning point here is to be gentle when cleaning out this grease as there are two delicate brush contacts in there. If you work around them with a cocktail stick, you can get the majority of grease out. In the other post that I plan to write, I'll explain what I think all these contacts are for - how the two speed wiper mechanism works. But for now, back to dismanting.... 

 

With the case cover and gear wheel removed, the worm gear of the motor shaft was freed up. Undoing two slotted screws  on the nose of the wiper body.....

....would eventually allow me to seperate the motor from the gear housing. But first I needed to do some undsoldering. At the solder points, I needed to frre-up the two wires that come from the within the motor body. BUT before you do that, first note which wire goes where.

 

On both my motors, there was a THIN wire in a white plastic sleeve connected to the solder point on the end - I'm going to call that solder point "A" for reasons I explain in my follow up post HERE. There was a THICKER wire in a brown woven sleeve connected to the middle solder point - yes, I'm going to call that solder point B'.

Now, these two wires  - the ones that disappear into the motor body  - are soldererd under the leads that connect the motor to the loom: - the short wires with male bullet connectors and coloured tags. So to un-solder the two internal wires means also unsoldering these other wires.  NOTE: you may find that  your red and blue tagged wires are not soldered in the same order as mine. I will explain this caveat in the next post I write. I suggest you take photos before you unsolder anything and, when it comes to reassembly, put your wires back where they came from.

 

Right, with that said, in my case, the wire soldered to point 'A' had a blue tag on it and the wire soldered to point 'B' had a red tag on it. A third wire connects the motor to the loom. That wire has a black tag and connects to a third solder point, closest to the eye through which these three wires pass. Call me conventional, but I'm going to call that solder point, 'solder point 'C''.....

With all these wires unsoldered, the two screws on the nose of the motor were removed. With a bit of wiggling, the heavy motor body and it's inards were gently seperated from the alloy gear housing. You may need to work the two wires you unsoldered backwards a little, to allow the motor to be pulled free.

Motor seperated from the gear housing

Behind the nose is the carrier plate for the two bushes that provide power to the armature. You will probably find that in wiggling the body free, the carrier plate and brushes have been dislodged from the commutator ring on the shaft and are now just around the shaft end. Because the brushes are spring-loaded, this might not be immediately obvious.

The brushes have slipped off the commutator

The brushes will need to be carefully relocated back over the commutator on reassembly. Also note in the photo above, the white nylon nipple on the end of the shaft. This is to help ensure the free running of the shaft. The nose cap also has a bronze or brass bush in it to act as a bearing.

 

The armature was removed from the casing from the gear end and I was able to examine the motor brushes.

The motor brush assembly

These were not too badly worn at all, but if you think yours need replacing, they are held in place by small coiled springs. I've got no idea what the sizes would be for replacement brushes.

The brushes are held by coiled springs

I cleaned the commutator on the armature. I think this is the best/ only photo I have. It's the shiny copper part in the background here.

Commutator in the background....

I spun it in my hand and used fine grade emery cloth to polish it up. I then carefully used a knife blade to clean out the muck between each segment.

The gear wheel was pulled free from the casing which was de-greased. I cleaned up and examined the gear wheel. 

Other than saying that you can see how the marks on the gear wheel line up to the two copper sweeper arms sticking out of the gear case, I will save any explanation of what is going on for my next post.

 

I didn't dismantle the motor any further. On the gear casing there was a small grub screw covered with a blob of blue paint.

The other end of the screw contacts a white plastic nipple on the worm gear end of the rotor shaft. It looks as though this screw is used to set the free play of the gear. I left this alone. Not least because the broken metal contact meant I would be using my spare gear casing.

 

I put clingfilm around the brush carrier to protect it and masked off the gear end of the body, then I stripped the paint off, de-rusted it and painted it up.I had planned to get the gear casing and nose vapour blasted to restore the 'just cast' look to the alloy but, given the bushes/ bearings in the two parts, and given how delicate the motor contacts seemed to be, I decided to put them in my ultrasonic bath instead. That was partially successful and removed some dirt but not as good as vapour blasting. I avoided the temptation to use metal polish on the alloy parts, partly because they were complex shapes and I wouldn't have been able to polish all areas, but mostly because it leaves the parts with a chrome-like finish - which I didn't want. 

I did indulge myself by having the triangular back and face plates re-coated in zinc after carefully removing the rubber seal. The back plate is hidden behind the dashboard but the face plate can be seen on the engine bay side.

Face plate with the rubber seal removed

 After that, it was back to reassembly. Which was basicaly the reverse of disassembly. I half-packed the gear case with light grease. Although the stuff I scraped out was dark and hard - like heavy grease - I suspect that it had just thickened up over the years. I tried Googling motor grease and concluded that a light grease should be good enough. 

I introduced the armature to the casing, making sure that the wires on the stator windings did not rub-on or obstruct the armature.

Make sure the winding wires are clear of the armature

    With the armature back inside the casing......

.....I used a screwdriver to push back the two carbon brushes against their springs and locate them over the commutator.

Note the irregular shape of the brush carrier. This is to hold it in the motor nose

I put a small dab of grease on the motor shaft where it would pass through it's bush. The ends of the two wires from the winding were threaded through, and out of the gear casing and the gear casing and body were  gradually introduced.

Pulling the two wires through the gear casing as I went, and holding the motor brushes on the commutator so that they did not slip off, I pushed the body and armature onto the gear casing so that the worm gear went to the bottom of it's tunnel and the motor body was flush with the casing. Note that there is a little tab on the motor body.

Note the locating tab (arrowed)

The tab corresponds to a cut out on the casing.

That means that the body only fits on the casing in a particular way. I suspect this is to line the wires up correctly with the hole in the gear casing.

 

I put a small dab of grease in it's bush and refitted the nose cone. There are 'keyed' cut outs in the edges of the brush plate that locate it in the nose cone. If the plate is not correctly seated in the nose cone, the nose cone will not fit correctly on the end of the motor body.

Note the irregular shaped ends of the brush carrier

Also bear in mind that you will need to line up the screw holes in the nose with their counterparts on the body. However avoid twisting the brush carrier as you fit the nose as you risk breaking or trapping a wire against the rotor.

 

I found it quite tricky to push the long screws through the nose and catch the threaded holes in the body. The rotational alignment of the nose is crucial and patience is needed to avoid cross-threading in the soft alloy gear casing.

At this stage, I just did up the two long screws just less than finger-tight. Before I went any further, I powered up the motor: I connected the positive of a 12v supply to the thick cable sticking through the body (the one with a brown woven outer) and the negative to the body of the motor. While it span, I adjusted the position of the cap and body relative to the gear casing to make sure the armature spun freely and without any scraping noises. Holding that position, I tightened the two screws through the body - continuing to make sure that the armature was able to spin freely. At the worm gear end I check for free play and decided that no adjustment of the small grub screw was necessary. Once happy, I disconnected the power.

I part filled the gear housing with grease. I greased the shaft of the gear and it's teeth, and refitted it to the gear casing cover, testing that it spun freely. I added more grease to the casing - leaving enough space for the gear but also not over-filling the housing. I refitted the casing cover and it's four screws - remembering to add a short extra flying earth lead. (In fact all I did was pinch the lead off my spare motor).

 

After refitting the triangular face plate and it's seals  - paying attention to the scallop edge of the plate - the last task was to re-solder all the contacts. Of the two wires coming from inside the motor, the thick wire in the brown woven sleeve goes to the middle of the three solder points. The thin wire in the white plastic sleeve goes to the first solder point - the point I labelled as 'A' earlier in this post. 

 

At the same time, I re-soldered the three colour-coded and bullet ended wires that connect the motor to the loom. As I said earlier-on that the connections on your solder points might be different to mine. On the two motors I have the connections are as per this 'before' photo:

The blue-tagged wire is first (my 'solder point 'A''), the red-tagged wire is in the middle (point 'B') and the black-tagged wire is at the end (point 'C'). BUT I SUSPECT THESE TWO ARE THE WRONG WAY ROUND. If your red and blue wires are the other way round, and your motor and wipers were working before you took your motor apart, I strongly suggest you connect your three wires up as they were before. 

 

And then onwards with refiiting. As the motor has been disassembed and the gear wheel moved/ removed, you need to find the 'park' position again......connect the positive of a 12V power supply to the black tagged wire connected to solder point 'C' and the negative to the motor body. The motor should run momentarily then stop - that's the 'park' position. 

I offered the face plate and motor assembly up to the hole in the bulkhead, then offered up the back clamping plate from behind the dash - again paying attention to the orientation of the scallop on one side. It should be along the top edge of both plates. The two plates were then bolted together and it simply remained to connect the motor back up to the linkage.

I fitted the short motor connecting rod over the splines of the motor shaft. If you marked the relative positions before, then re-align those marks. Here are mine again:

Reference marks on the shaft and connecting rod

The connecting rod should be at about a '4 o'clock'' angle. I refitted the nut but did not fully tighten it at this point. I aligned the wiper linkage so that the control rod overlaid the connecting rod. 

 

If yours doesn't overlay it, pull the motor connecting rod off the splines of the motor shaft and move it until the two do align. If you are having trouble with this step, it might be worth checking that your motor is in the 'park' position.

 

I was satisfied with my alignment, and tightened the nut holding the motor connecting rod to the motor shaft. I greased the nylon socket and pressed the control rod end over the knuckle of the connecting rod. I sourced and fitted a securing circlip.

That's pretty much it, but read on......

 

With the dashboard out it was difficult to check that everything works as intended from the dash knob. So I used a portable 12V supply to test functionality.........

Testing functionality....

......and my wipers didn't work! 'Park' and 'slow' worked as intended, But in the 'fast' position there was a current draw but the motor didn't turn. I remember at least two other people with a wiper problem where the motor got hot and this could be the scenario that led to that.

 

I was sure I had resoldered my colour-tagged wires back as they had been removed, but  I found I had to reverse the red and blue connections from my power supply (so that blue from the switch and loom went to the middle solder point) to get both wiper speeds and 'park' to operate correctly from the switch.

For me, blue and red connections reversed restored correct operation

For the moment, just know that if you find the same problem, this doesn't stop your motor being refiitted or stop it working as intended. As I found out, you just might need to swap the red and blue wires over at their plug connections or where they join the switch behind the dashboard. And if you want to keep all your colour coding correct, once you've swapped your wires, just swap over the coloured tags as well so that red still connects to red and blue to blue. That's what I did!

 

I'll revisit all of this, and more, in my next post on the mysteries of the wiper motor........