Automotive switches are normally sealed or self cleaning because of oxidized oils, brake dust, road dust, pollen, silt, soot, dead skin, fabric fibers, hair, etc. People make a mess of their car using cheap silicone leather and dashboard cleaner but that shouldn't ruin important switches.
Sniff the love: Subaru's SUVs overwhelmed by scent of hair shampoo, recalls 2.2 million cars
Japanese automaker Subaru has told the US National Highway Transportation Safety Administration that it plans to recall some 1.3 million vehicles in the US because of emissions problems. It plans to do the same elsewhere in North America and in Japan, bringing the recall total to around 2.2 million. The issue isn't vehicle …
COMMENTS
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Saturday 2nd March 2019 17:51 GMT Paul Crawford
I suspect there might be a more serious reason than brake lights not coming on - maybe this is also the means to disengage the cruise control?
As other commentards have already mentioned, most likely it is a "new" designer that lacks the knowledge that most switches are not suitable for near-zero current and so you need to have some significant current (by microprocessor interface standards, only a few mA in most cases) to make it work reliably. You get (or used to) more expensive switches with gold flashing for "dry" switching, but then they are not suited to high currents as it blows away the few um of gold.
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Monday 4th March 2019 17:40 GMT ckm5
That's simply not true, switches inside cars are almost never sealed. I have been working on cars for 30+ years and I don't think I've ever seen a car with fully sealed switches.
As far as 'self-cleaning', that sounds like a bunch of marketing hype. Yeah, terminals probably scrap of the gunk, but that's hardly a design feature.
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Saturday 2nd March 2019 12:46 GMT Down not across
Re: Progress?
Could it be that LEDs don't draw enough current?
Not only that. You got things like BMW's LCM (as an example) where all lighting is controlled via a module rather than direct from switch so current draw on many switches is unlikely to be that high these days even without external lighting changing to LEDs.
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Monday 4th March 2019 13:07 GMT Anonymous Coward
Re: Progress?
I'm just waiting for the day when there's an idiot tailgater a metre or two behind me and something comes out in front of me. (Or a leaf blows across, or a dog/pedestrian, etc.)
They're going to be part of the rear end of my car before I even realise the Autonomous Emergency Braking has activated...
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Monday 4th March 2019 16:52 GMT Orv
Re: Progress?
Pressure-operated brake light switches were a common thing on older vehicles -- usually sharing the same switches used to trigger the brake warning light if pressure was lost in one circuit. They're not favored anymore because they cause more of a lag in turning on the brake lights, and it's often possible to brake lightly without triggering a pressure-activated switch.
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Monday 4th March 2019 21:52 GMT Fungus Bob
Re: Progress?
Not just BMW. Chrysler products have used a Body Control Module to control every switch, light and gauge not directly running the engine or transmission for years. Fuel level, brake lights, headlights, door locks, windshield wipers...
I suspect most carmakers do things this new and stupid way.
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Saturday 2nd March 2019 08:57 GMT Pascal Monett
Holy cow, it's everywhere
So now I learn that we emit potentially noxious gases simply by wanting to stay clean and smell nice. Terrific. What other doomsday mechanism will our consumer society dump on our ignorant hides ?
It might be time to slow things down a bit and not rush to production with every half-baked idea simply because we can.
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Saturday 2nd March 2019 09:42 GMT Mike 125
Re: Holy cow, it's everywhere
The Precautionary Principle isn't popular in our neo-liberal culture. Our overlords tell us we must all have the freedom to consume, pollute and degrade. It's our human right. Actually, our it's our duty, they say.
Meanwhile: Ooooh, glyphosate’s on special offer at B&Q, quick let’s get down there in the Subaru.
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Saturday 2nd March 2019 10:02 GMT Andy Non
Re: Holy cow, it's everywhere
"simply by wanting to stay clean and smell nice."
If humans still exist in a hundred years, society will look back in horror at some of the stuff we put on/in our bodies. Like we look back to Victorian times in horror at people bathing in radioactive radon baths or women putting white lead based cosmetics on their face to have a paler skin or sprinkling talcum powder on your body laced with asbestos dust. Lovely.
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Sunday 3rd March 2019 18:28 GMT Jeffrey Nonken
Re: Holy cow, it's everywhere
Personally, I find most perfumes and artificial scents obnoxious, if not downright noxious. One man's "smell nice" is another man's anaphylaxis.
And before anybody gets snide: I shower daily with tea tree oil soap and Aussie brand shampoo, and change to clean cotton underwear (washed in unscented detergent). I don't get complaints.
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Saturday 2nd March 2019 10:28 GMT Anonymous Coward
This is what happens when you implement diversity and equality...
Women wearing every lotion, perfume and powder under the sun building cars. No wonder they get contaminated. I expect there's reams of long girly hair everywhere too. And those damn hair grip things.
It isn't right, I tell you. Let's hope this nonsense stops after Brexit. And don't get me started on that Davina McCall.
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Monday 4th March 2019 14:52 GMT vtcodger
Re: This is what happens when you implement diversity and equality...
I still find at least one bobby pin every couple of months from the previous owner.
Bobby pins are thought to be a stage in the complex life cycle of an obscure and poorly studied organism. They seem to appear spontaneously, but actually are the spawn of wire coathangers that have been stored near a phone that is exposed to repeated robocalls. Left alone in the dark, they will eventually morph into single socks that do not match any other stocking you own or have ever owned,
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Saturday 2nd March 2019 12:44 GMT Anonymous Coward
Not necessarily
If you read switch specifications very carefully - as you do when designing any electromechanical product - you will know that DC switches have a minimum as well as a maximum current. Below the minimum current, there may not be enough cleaning action from the current itself to keep the contacts working.
I wonder if this issue is due to the switch being designed in the days when the brake (note spelling) light switches drew the entire lamp current, and now all that goes through is the small current needed for whatever the logic input is to something on the CANBUS.
Sealing switches is not always a good idea because any arcing can cause deterioration of the insulators, which then deposits crap on the contacts. For logic interfacing, sealed reed units are best because they are glass/metal only. But they are very limited in current and can't be used for direct lamp switching.
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Saturday 2nd March 2019 13:13 GMT David Pearce
Re: Not necessarily
Unfortunately they don't teach the need for a wetting current at university these days. Most cars use some sort of micro switch with plunger for this sort of application
A quick sample from Omron shows something like 1mA at 5V as a minimum ie 4k7, a surprisingly low value for the average fresh engineer.
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Saturday 2nd March 2019 16:08 GMT TonyWilk
Re: Not necessarily
My company was caught out years ago by silicone contamination of low voltage low current connectors, grease was used to exclude moisture but in a few months micro fibres of silicon/silicon carbide? grew and insulated the contacts. Cleaning the stuff off and replacing all the connectors was entertaining!
Safe levels of silicone contamination for electrical contact:
https://ieeexplore.ieee.org/document/489686
Yours,
TonyWilk
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Saturday 2nd March 2019 21:21 GMT Francis Boyle
"it appears that Subaru have tried to save a few dollars per car by using a cheap component"
Or a theoretically better component. The theories bruited above remind me of the problem of LED traffic lights not producing enough heat to melt snow. It can be seriously non-obvious that the effective working of a system relies on some unintended and unnoticed side effect of the operation of a single component.
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Monday 4th March 2019 09:29 GMT imanidiot
The theories bruited above remind me of the problem of LED traffic lights not producing enough heat to melt snow.
Not really a problem most of the time. And easily solved by including a small heater that is only switched on at sub zero temperatures (This is still more power effective than incandescent bulbs). Alternatively I've heard that even just applying a non-stick coating to the lenses is enough. It's just that for the early models nobody ever thought it could be a thing.
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Monday 4th March 2019 18:19 GMT jtaylor
Re: pedal area
My clutch pedal started squeaking and groaning. I cured that with a few shots of silicone grease where the pedal arm rotates against the bracket. (Silicone grease won't destroy the hydraulic seal that's exposed a few inches behind this.)
I'm not the first person to do this.
I really hope I didn't create electrical problems under the dashboard.
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Saturday 2nd March 2019 14:25 GMT Anonymous Coward
smells like
Environmental factors like the shampoo the car's driver uses or the brand of hand lotion used by the tech building the car seem far fetched. A much higher possibility is the use of an adhesive that contains silicone on a part in close proximity to the failing switch. That would give 24x7 exposure instead of brief or intermittent exposure. Given the fact that this is an automotive environment, I'd also wonder about seals, gaskets, etc.
It's surprisingly common to see assembly notes on PCB prints calling out the use of silicone epoxy to secure bulky components (including switches and relays). I suspect that adding adhesives is sometimes done in a rush late in the design cycle after a product fails vibration testing.
EEs do have a tendency to forget about contact wetting currents (source: I are one, and I do forget about them), but we're even less familiar with chemistry. Try finding wetting current specs on a relay datasheet. They're usually there, but buried. Now try finding the warning about not exposing the device to silicone. That's usually buried in a app note somewhere.
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Monday 4th March 2019 19:36 GMT paulll
Re: smells like
Armor-All's probably equally plausible.
But having owned a few North American vehicles of the 'his' variety (ie, manual), and forced to get up and under there with a torch to find and short the stupid clutch interlock switch, some cars look like an,"Alien," nest up there, and I'd guess it's silicone grease for the reasons mentioned above; I'd be surprised if some of the stuff *didn't* wind up where it's not meant to be.
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Saturday 2nd March 2019 23:54 GMT Mike 16
Young'uns and switches
Concur with the various mentions of minimum current. Once was a time when _serious_ switch interfaces made sure the combo of pullup resistor value and the B+ on the other end kept things shiny :-)
But it's not just the folklore on electrical stuff that gets forgotten/ignored. After several sessions of an EE lying through his teeth about a particular switch being readable at all (despite being on the 10th bit of an 8-bit port), I got to confront the physical design. The ME had used a stamped lever to bear directly on the little button of a PCB-mounted microswitch, rather than the must-be-50-years-old practice of having something with a bit of compliance between the fragile, low-travel switch and the big-bad-world of industrial equipment. But by the time I could get anybody to listen (Go away, Gramps, you're just a programmer), it was too late, so they just edited the spec-sheet to no longer promise any mitigation of that particular failure mode.
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Sunday 3rd March 2019 13:55 GMT Korev
Another possibility?
Could the source of the silicone be... Bulgarian Airbags?
Silicone or leather? Who knows -->
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Monday 4th March 2019 09:33 GMT imanidiot
Sure, blame the customer
I have a hard time believing the output from the cars occupants (no matter how noxious some people can be with their creams and perfumes) can affect a brake switch that low down in the car, in a usually well ventilated (by the lower heating/ventilation ducts) area. More likely it's something used in the fabrication process, combined with a poor switch design (as highlighted above).