109 Wipers

Ever since the big rebuild, the wind screen wipers have been prone to over-sweeping on a wet screen, especially at high speed.  I thought it might be due to worn wiper arms or spindle boxes, so they were replaced with brand new Genuine Parts some time ago, even though new parts had been fitted during the rebuild, but to no effect.  Today I replaced the Britpart cable fitted during the rebuild with a new Gen Parts cable.  The Britpart cable had been too long on fitting, so I had cut the end off.  I suspected that this might be allowing the helical wire to compress and stretch like a coil spring, allowing excess wiper movement ion the wet screen and reduced movement on a dry screen. 

Fitting the new genuine cable had the same problem – the cable is about 12″ too long, extending well beyond the cable guide tubes and out through the door aperture with the right hand door open and the dash end panel removed.  So, the new cable had to be cut down like the old one.  I crushed the last few wraps of the coil onto the inner cable with the vice to make sure that it can’t spring, so it may improve matter slightly, but I’m not holding my breath.

To remove and replace a cable, the process is pretty simple.  Remove the wiper arms from their spindles and the wiper motor cover (left end of lower dash – the black vinyl covered piece with three screws to the bulkhead on a  SIII, or a square pressed plate with four screws on a SIIA in the same location).  With the panel removed and the wiper motor exposed, disconnect the electrics and on the SIII remove the black plastic tubular trim that covers the cable run, if it didn’t come away with the motor cover.   Then undo the screws of the clamp holding the motor to the bulkhead and the 3/4″ nut securing the top of the motor casing to the operating cable guide tube.  Then withdraw the motor, pulling the entire length of cable out of the tubes with it (that’s why the wiper arms had to come off).

The back plate is held onto the casing with four hex-headed screws.  Remove these, and the cover can be separated.  This exposes the interior mechanism, which constitutes a worm gear driven directly by the motor, a wheel gear with an offset pin, a coupling that connects that pin to the end of the cable, and the cable end.  The coupling us held to the pin with an E-clip.  This can be prised off with screw drivers.  With the clip removed, the coupling can be withdrawn, followed by the cable.  The cable passes through a piece of the casing which will come away with it – transfer this to the new cable if you are replacing it.  On the other side of the main casing, you will see the end of the gear wheel’s shaft.  This is retained by another C-clip, which can be prised off in the same way as the interior E-clip.  This allows the gear to be removed from the casing.  This exposes the plunger of the park switch, and on the gear wheel the raised plastic platform which operates that plunger and switch.  There is also a plastic sleeve for the cable end to slide up and down, which can be removed from the casing.  Be careful not to lose the clips, the large washer that sits under the outer C-clip, the smaller washer that sits on the gear wheel’s pin before fitting the coupling, or the white plastic bush that sits in the pin hole of the coupling.

Clean all the parts up and inspect them for wear and damage.  I found a tiny amount of end float between the worm gear (with a nylon bush on its end) and the float control screw through the casing, and a touch of slack in the mesh of the gears, but I suspect these are normal.  Everything else was good.  As always, assembly is the reverse of stripping, making sure you remember to apply some grease to the moving parts inside the motor casing.  You can refit the gear wheel in the same orientation it came out, but it shouldn’t really matter – the motor will still cut out when the gear wheel reaches the park position, regardless of the position of the worm gear, so the operation of the motor will be identical, regardless of the position in which you fit the wheel on assembly.  Just remember to operate the motor and let it self park before refitting the wiper arms to the spindles.

The result of all this work appears to be… nothing.  I have yet to see what happens at high speed in rain, where the wind on the screen and the reduced friction on the glass have been combining to cause the over-sweep, but a test on the drive way with the screen washer and wipers appears to be similar to before the new cable was fitted.  There just seems to be too much play in the wiper spindle units and their mesh with the cable, and given that they’re only a year or so old and the previous units were about five years old and showed no signs of wear when I stripped them, it suggests the system is just not able to be assembled free of slack and slop.  It means that I will have to live with wiper blades banging against the wind screen frame, making an irritating and unwelcome noise and damaging the wiper blades.  The next course of action may be to bond medium-soft rubber blocks onto the windscreen frame to act as buffers to the wiper blades.

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Comments

  1. Hi, I’ve just transferred my own wiper mechanism from the old bulkhead of my SIII to a new one. It’s had no servicing of any kind since before I purchased the vehicle 15 years ago. Before removal, I found that the pipe from the motor to the passenger wiper arm mechanism was loosely clamped at the wiper arm end, this did allow some play in the wiper arms.
    I made sure all the pipes are securely located and clamped when I refitted it, and now have no noticable play in the arms, but the nuts that hold them together are not nyloc, had no spring washers, or other anti-shake treatment, and wiper fittings will shake with every use. I’ll add some threadlock before fitting the upper dash to be safe.
    Have you checked the arm mechanisms on yours. It does need more disassembly of the dash than changing the cable, but worth a look if you have time.

  2. Thanks Ian.

    I have checked them – I used brand new Britpart boxes on the rebuild and replaced them again with brant new Gen Parts boxes a couple of years ago. The nuts are nylons and were done up nice and tight, and the cable guide tubes are solid. I used new knurled adapters on the spindles and new arms, too. The arms have a small amount of movement in their pivot rivets, but there is also movement at the spindles. It’s pretty small, and the good news is that the new cable has improved things, though not cured the play, while driving. It’s better than I thought it would be after testing for play by hand.

    Nick

  3. Wouldn’t you know it, mine have started to over sweep this week. I only replaced the spindles with new ones last year. I knew I should have replaced the drive cable when I had the dash apart doing the heated washer jet mod, run out of time on the day though.

    I think I’ll fit the new drive cable and turn the spindles through 180% when I take the dash apart to fit the heated mirror wiring.

    Regards,

  4. Hi Nick,
    I see you have the defender type grab handle fitted between the lower dash / wiper motor cover and the dash top.
    I’ve aquired one of these, but it doesn’t seem to fit well with the series 3 dash top.
    Is your dash top a series 3 item or a defender one? Did it take much work to make it fit?
    (I’ve scoured your archives, and found a lot about ypur work on the lower dash, but nothing on the top part or the grab handle.)
    Thanks again,
    Iain

  5. Hi Ian.

    The Defender top dash is shallower than the SIII’s, so I had to trim the handle piece to allow the top dash to protrude form the top corner and cut a corresponding section of the old SIII end trim to cover that protrusion. You may need to drill a hole in the wiper cover box for the handle’s lower dowel.

    Nick.

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