Why no automatic wipers on rear windows?
Discussion
Automatic wipers are (for the most part) controlled by an optical sensor which fires infrared at the windscreen and measures how much is refracted away by water on the surface. I imagine this would be a pain in the arse to implement on the rear windscreen because
a) the sensors are pretty expensive
b) it mists up a lot more often and isn't such a priority for the driver to keep clear
c) it gets far dirtier and, again, isn't such a priority to clean
d) not so much rain hits it directly anyway, so it would need setting up totally differently (with the associated development costs) or have a frustrating delay
e) you don't have a rear-view mirror mounting to disguise the sensor behind, so it'd take up visibility
And you wouldn't want the rear wiper to be driven by the same sensor as the front ones, because of c) and d). Interesting thought, though.
a) the sensors are pretty expensive
b) it mists up a lot more often and isn't such a priority for the driver to keep clear
c) it gets far dirtier and, again, isn't such a priority to clean
d) not so much rain hits it directly anyway, so it would need setting up totally differently (with the associated development costs) or have a frustrating delay
e) you don't have a rear-view mirror mounting to disguise the sensor behind, so it'd take up visibility
And you wouldn't want the rear wiper to be driven by the same sensor as the front ones, because of c) and d). Interesting thought, though.
McSam said:
a) the sensors are pretty expensive
b) it mists up a lot more often and isn't such a priority for the driver to keep clear
c) it gets far dirtier and, again, isn't such a priority to clean
d) not so much rain hits it directly anyway, so it would need setting up totally differently (with the associated development costs) or have a frustrating delay
e) you don't have a rear-view mirror mounting to disguise the sensor behind, so it'd take up visibility
...but apart from that...? b) it mists up a lot more often and isn't such a priority for the driver to keep clear
c) it gets far dirtier and, again, isn't such a priority to clean
d) not so much rain hits it directly anyway, so it would need setting up totally differently (with the associated development costs) or have a frustrating delay
e) you don't have a rear-view mirror mounting to disguise the sensor behind, so it'd take up visibility
It would be really useful on some cars. On the first Jazz my missus had there was no intermittent rear wipe, which was a pain. The newer one has it, but on streaming wet roads it could do with being on continuously.
I fitted a variable intermittent unit to the rear wiper on a Capri many years ago - worked a treat.
Hackney said:
Auto-off would definitely be a good idea especially given the number I see still on when it's perfectly fine.
Look in the rear view mirror much?
Does this irritate anyone else?Look in the rear view mirror much?
Worse still, I remember being in a work mate's car for a 20 minute journey some time ago. It was dry the whole way but he had the front wipers on intermittently for the entire trip.
He's an idiot but even so, come on.
McSam said:
d) not so much rain hits it directly anyway, so it would need setting up totally differently (with the associated development costs) or have a frustrating delay
The rear window on an estate car gets misted up quickly at motorway speeds, but the fixed intermittent wiper delay is never ideal. Always too early or too late.I can't believe it's an issue of cost, since manufacturers are able to offer automatic front wipers relatively cheaply these days. I just wonder why don't they offer a similar option for the rear?
Absolutely everything in the modern automotive industry is an issue of cost, more than you could possibly believe!
Just a few moments' thought led to a pretty long and convincing list of practical reasons why it wouldn't make much sense to implement, but going further, is there a genuine customer need for it? And if there is, why doesn't anyone offer it? Automatic wiper tech has been around for more than fifteen years now, and if any OEM thought enough customers would tick the box to make it worth developing a semi-decent solution for the rear screen, it would already be out there.
Rain sensors aren't just expensive parts themselves, their implementation is a massive pain too. They're single-use items and need to be applied carefully, adding to assembly time and scrap costs. Suddenly you need to have two different screens on the line, which makes even the standard one more expensive by reducing its production volume, you need to accurately estimate demand for each type, make sure the build procedure is robust for both types, the list of ballache goes on and on so you need to be REALLY sure it's going to sell you more cars. I don't even think it'd work very well without big investment, never mind generate more demand!
Just a few moments' thought led to a pretty long and convincing list of practical reasons why it wouldn't make much sense to implement, but going further, is there a genuine customer need for it? And if there is, why doesn't anyone offer it? Automatic wiper tech has been around for more than fifteen years now, and if any OEM thought enough customers would tick the box to make it worth developing a semi-decent solution for the rear screen, it would already be out there.
Rain sensors aren't just expensive parts themselves, their implementation is a massive pain too. They're single-use items and need to be applied carefully, adding to assembly time and scrap costs. Suddenly you need to have two different screens on the line, which makes even the standard one more expensive by reducing its production volume, you need to accurately estimate demand for each type, make sure the build procedure is robust for both types, the list of ballache goes on and on so you need to be REALLY sure it's going to sell you more cars. I don't even think it'd work very well without big investment, never mind generate more demand!
I have hardly any OCDs apart from being behind one of these. It really really unnecessarily irritates me to the point that I have to either overtake or let someone overtake me so I don't have to view it.
And if I'm behind one of these when stuck at a red light then my skin starts to crawl
Can't really explain it
And if I'm behind one of these when stuck at a red light then my skin starts to crawl
Can't really explain it
When the rear wiper is switched on in my Punto it's intermittent and goes off every other wipe of the front ones which seems to do the trick. It also self selects when you put the car in reverse with the front ones on too. And the gap between the intermittent wipes gets shorter the faster you go. All together this seems to cover most of the bases.
I've driven a few cars with automatic wipers and have always ended up switching them on and off manually as there's too much or too little water on the screen. They make me think of automatic shop doors, not quite automatic enough...
I've driven a few cars with automatic wipers and have always ended up switching them on and off manually as there's too much or too little water on the screen. They make me think of automatic shop doors, not quite automatic enough...
Sheepshanks said:
On the first Jazz my missus had there was no intermittent rear wipe, which was a pain. The newer one has it, but on streaming wet roads it could do with being on continuously.
This is a far bigger pain in the arse - sometimes, you want it intermittent, sometimes, you want it constant. It should not be hard for manufacturers to cater to that. NOT one or the other.Mind you, if they got the bloody aerodynamics right in the first place, it'd be far less of an issue...
crazy about cars said:
Jimmyarm said:
elephantstone said:
When i have the wipers on and select reverse the rear wiper automatically wipes if that counts? Car is 2010 Audi A3.
Mine does too. 2000 Vauxhall Corsa 
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