as David mentioned, there has been a change of wiper system between SII and SIII: both SI and SII use “off-screen parking” to speed up wiping while in use (in fact, the wiping angle is reduced) and allowing improved visibility while not in use. When parking the wipers it looks like they were trying a rumba … This feature depends on the reverse action.
For whatever reason (lack of reliability? cost?) it was abandoned for SIII. As Carl wrote, parking is still an issue with SIII wipers.
Wrong, the swept area is the same, they sweep the same area of the screen and then park further out of sight. So in a way, they reach more of the screen where you actually need it, and get out of the way further. Very nice, although it is a bit complicated when they reverse and wipe ⅔ of the screen for the last wipe before they ultimately park with a satisfying clunk right at the bottom of the screen.
I have learned not to like how they’re parked on the S3 - probably mostly needed because the (very useful) interval and single swipe settings have to run in reverse and it wouldn’t wipe the whole screen, because the wiper would already have extended the swipe into the park position.
By definition, the angle between the parking position and the regular return position in operation (“off screen”) is omitted for regular operation. Hence the angle covered in regular operation is lower than if the wipers were returning to the parking position during every cycle. Note that the term “off screen” doesn’t relate to the windscreen itself: even “off screen” the wipers still park on glass. “Off screen” relates to the field covered during regular operation (say betwen 10:30 and 2:30). So it would easily be possible to include the parking position into the operative sweep. Yet, as the lowest 5° (?) are not very helpful for visibility, but excluding them speeds up operation by + 10 % may have convinced the engineers …
Kind of, but not easily.
The sweep is, say, 120°. The sweep in the park operation is also 120°, the passenger side stays wet.
The park position is so low that the wipers would hit the trim if the wipers were running in the park position, especially on fast.
A 140° gear would theoretically wipe more screen area but why didn’t they do that in the s3? Probably as you say, it wastes time. And why didn’t they make the middle wiper blade a bit longer?
Probably a question of parts supply mostly. And why make it more complicated if all you get is a better view of the bonnet. The car was probably finished with the parking wiper motor in mind, and it clears a symmetric field.
I really don’t know, David. But it seems ‘unprofessional’ to operate an electric switch during normal wiping when it is not needed. And reversing the motor to activate the switch when parking seems eminently reasonable - I just don’t know how…
Well, at first and someone correct me if that is wrong, the switch was activated every time. For parking power went through the switch.
Then, the park position was introduced and activated by reversing the motor. The extended throw activated the switch.
Then, the parking position was deleted and they had to come up with the (sort of unprofessional ) ramp that activates the switch only in reverse. Why they didn’t just revert to the early system is very unclear to me at the moment.
The rack is driven by the excentric pin on the gear, and with the motor running the sweep is the same no matter what?
Slack and wear over time, and old grease, may interfere with the swept area, and may give less than perfect operation. The blades/arms can easily be repositioned to any position - but the sweep itself is set.
As an aside; the wipers should be set to self-park on the driver’s side - LHD or RHD setting; this gives the driver maximum clear view. On the passenger’s side a larger section of the screen is then inevitably left unswept - better than in front of the driver with the wrong set-up…
Is that a S3? All the series 3 cars including left and RH Drive i have seen park on the passenger side unlike the S2 which park on the drivers side. Have you changed it?
No, that’s a S1… but on the S3 the wiper motor is always behind the battery, same as the S1 - indeed my RHD S3 had the wipers parked on the left or passenger side. Somehow that got swapped around. Weird, right?
I don’t know how it’s done exactly, but obviously either the first sweep from the parking position must cover a greater angle than the following sweeps covering the regular field of view, or - as David’s vid seems to advocate, the first return sweep must be shorter than the following. As regards the “why” I’d still favour the wiping frequency theory as a justification for the complicated design. It would be easy to position the wipers, say, one inch above the lower chrome trim, and I doubt the wipers would overrun the trim.
The logic for changing the system with SIII might be as follows: the main purpose of off-screen parking was to both allow for “clear view upon first sweep” (commanding the resting position before the driver (btw Porsche did the same thing on 911s) while not interfering with (not so tall) drivers’ visibility. For SIII cars they may have abandoned the first goal, resting wipers in front of the co-pilot, rendering off-screen parking superfluous.
BTW, wiper operation on series XJs is peculiar in that it is fully symmetrical. Most cars with two wiper let the driver’s side wiper travel end with the outer edge of the window, which requires different axle setups for RHD/LHD.
It cannot do that, Jochen - the sweep angle is constant; from one extreme position the wheel and excentric pin rotates 180 degrees to the other extreme - then back again.
One conceivable variant is that from ‘park’ position at start; the motor/gear continues to rotate past the self park position - which would just move the initial sweep area slightly, but the sweep angle as such cannot be altered…
or - as David’s vid seems to advocate, the first return sweep must be shorter than the following. As regards the “why” I’d still favour the wiping frequency theory as a justification for the complicated design.
Cost, cost and cost are the reasons car manufacturers change/delete items at series changes.
All facelift cars are cheaper to produce than the version they replace.
Having an additional gearbox to give lower parking, but a messy first and last sweep, does seem like an extravagance too far.
Just change the wiper crank to give a greater sweep angle and be done with it.
This is S1, and parking in front of the driver. Different for the S3.
It’s 0-1-0(stuck)-2-0. apart from the sticking brush that caused them to stop the wipers are operating correctly, and self park correctly.
Frank, I see your point. Nevertheless, with off-screen parking the wipers have to cover a bigger angle once when starting and once when stopping. Of course, you’re right: the pin on the gearwheel transforming the rotation into a go-return movement has a fixed position. I can only guess that the additional way is achieved by an additional change of direction.
[quote=“Jochen_Glockner, post:39, topic:443603, full:true”]
I can only guess that the additional way is achieved by an additional change of direction.
Let me also guess, Jochen…
The effect shown can be achieved by a slider block/arrangement. With the motor rotating one way the block/arrangement is in one position - rotating the opposite way it moves to the other position. This will not alter sweep angles, but will displace the angles as shown in the video?
‘Selfparking’ in itself was just to ease drivers load in paying attention to position of the wiper blades when stopping the motor. But it sure complicated the electrics…
