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Sherlock Ohms

Brake Lights Were on the Blink

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naperlou
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Blogger
Re: auto diagnostics
naperlou   1/7/2013 9:42:34 PM
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William K: I have to disagree with you there.  For one thing, there are at least 50 microcontrollers in a car today.  It is often much simpler to put in another microcontroller than trying to integrate software within a central processing unit.  Since many of the components come from other manufacurers, or even other divisions of a car company, this makes sense.  As for cost, even simple electromechanical are very expensive.  My wife and I recently replaced the automatic door lock actuators in a minivan.  I think they were between $50 and $100 apiece.  And we installed them outselves.  I was a fun project.  On the other hand, these were simple relays.  There are many reasons for the high cost of automotive parts, but not having access to the code is not one of them.

William K.
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Re: auto diagnostics
William K.   1/7/2013 10:10:38 PM
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It is almost always "easier" to stick in a micro controller  and put in some code than to do any actual engineering. No question about that. BUT the unintended consequences of code that it is unable to handle exceptions, or does not handle the way some users think, and is generally not exactly the best choice. That is the fundamental flw that I see in using software to implement many functions. Primarily code is only written to handle what the programmer believes will happen, which is usually a very small subset of the real world.

dbues
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Gold
Re: auto diagnostics
dbues   1/8/2013 8:26:26 AM
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Here's a counter to your proposal for using inexpensive microcontrollers....

We were driving our 2000 Pontiac Montana minivan one day when somebody started flashing their lights at us from behind.  We asked what was the matter and they said our brake lights were out.  That was strange...in 40 years of working on cars, I had never had BOTH lights go out at the same time.  Funny thing is that the high-mounted center brake light still worked.

I replaced the bulb on the right side and...NOTHING!!!  Same on the left.  We called the dealer and they laughed saying, "Oh that must be the controller board."  Funny thing that, for over 50 years, a switch was good enough for controlling brake lights, but NOW you need a controller.

I don't drive GM anymore....

3drob
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Platinum
Re: auto diagnostics
3drob   1/8/2013 9:52:08 AM
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Back in the 1990's (I think) Chrysler wired their stereo's into the vehicle's CAN bus.  Problem with that was that when the radio failed, the whole vehicle shut down and needed a tow back to the dealer.  Seemed like a good idea at the time.

Not only is it harder for DIY auto repair because of the proprietary nature of the components, but because these components interact in complicated ways.

Only legislation requiring manufactures to publish technical spec's on their components (and their component's intended/expected behavior) will improve the situation for the consumer.  Thankfully we have the internet and youtube.

Tool_maker
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Platinum
What is the big deal?
Tool_maker   1/8/2013 1:06:56 PM
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  I was a comfirmed DIY for years. Points & plugs every 12,000 miles. Oil every 3 and filter every other change. Air filter at 12,000 when the plugs got changed, etc. We do not have to do that junk nearly as often any more. So the brake light switch went bad, big deal. Both mechanical and elecrical parts fail on occasion, and need replacing.

  Autos are so much more dependable than years past that when something does go wrong it is worthy of a magazine article. It wasn't that terribly long ago that a vehicle with 75,000 miles on it was almost always ready for the salvage yard. I have fond memories of my first decent car, 1962 Buick with a 401 cubic inch engine,and AFB carb. I would love to have it back. But, I would not want it as my primary mode of transportation, because I am no longer willing to spend every other weekend working on a car. Or at least that is what it seemed like.

Critic
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Platinum
Re: What is the big deal?
Critic   1/9/2013 9:34:53 AM
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I agree.  What's the big deal?  Finding and replacing a bad brake-light switch doesn't require too much diagnostic effort.

On the other hand, it did get us all started writing these silly messages that we enjoy so much!  Thanks, John.

One thing that puzzles me is why a Volvo engineer would write about replacing a bad switch.  Certainly there must be something more interesting in his work that would be more interesting to readers as well, but maybe Volvo won't let him publish.

Critic
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Platinum
Re: auto diagnostics
Critic   1/9/2013 9:37:52 AM
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More legislation we do not need.  Speak with your wallets!  Don't buy cars you don't like because you can't easily service them yourself, or because parts are too expensive.

Critic
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Platinum
Re: auto diagnostics
Critic   1/9/2013 9:43:53 AM
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@JimT:

Mounting a PCB directly against a metal housing, with only solder mask as insulaiton is a bad, bad idea from a reliability perspective.  All it takes is a pinhole or crack in the solder mask, and a little corrosion (or a little whisker/dendrite), and a short will develop.  Thermal expansion/contraction could also eventually scuff through the solder mask.  Space the board off the housing or use robust insulation.

More than one person has tried to mount a computer motherboard directly into a computer case with no standoffs.  Guess what happens! 

3drob
User Rank
Platinum
Re: auto diagnostics
3drob   1/9/2013 10:04:25 AM
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As a closet libertarian it pains me to say, but yes Virginia, we need more legislation to protect the consumer.  Car companies do the things they do to maximize profits for their shareholders and stakeholders (dealerships).  Then they worry about the labor unions.  Customers come last.  In a cut-throat environment like the auto industry, there are NO new cars that I know of that are easily/cheaply servicable any more.  Certainly such creatures (even if they did exist) wouldn't inspire a blog post here (an example of what you won't read here:  "I changed my spark plugs last week, I could reach them all w/o lifting the engine or contorting my body, and it took 15 minutes",  yawn.)  I would interested to hear any examples of cars that are easy/cheap to service.

But, as an example of "good" legislation:  look at the OBD ports in ALL modern cars.  Such a thing would NEVER have existed without that legislation. In any case, legislation evens the playing field and allows/forces car companies to do the right thing without going bankrupt.

Tool_maker
User Rank
Platinum
You are right
Tool_maker   1/9/2013 12:56:44 PM
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  Critic: You are correct and seldom do all the comments pertain directly to the original post. I learn things from some of the splinters and that makes these forums enjoyable. I guess my gripe was that when something fails it is not always a mistake. Sometimes things just wear out from repeated use and few of us would be willing to pay the price of a vehicle in which everything is built to last through eternity, even if that was possible.

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