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4hv.org :: Forums :: General Chatting
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Bad Design or Just Me

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genious 7
Wed May 02 2012, 02:20AM Print
genious 7 Registered Member #2887 Joined: Sat May 29 2010, 11:10PM
Location: Panama City, Panama
Posts: 107
Recently, a friend of mine brought me his girlfriend's car's air conditioner panel for repair. They had kicked the air conditioner switch and it had broken off. It was just a matter of gluing and soldering again; but the design used consisted on the rotatory switch PCB area held by five 1mm links to the rest PCB. (dont really know how to explain it; see pic)


1335924739 2887 FT0 Img388


--Oh, and those holes on the broken switch are not screw holes; the switch was held entirely by those links in the PCB--

Why would they to that? I see no benefit for the grooves other than requiring more tooling and weakening that area; do you think it is planned obsolesce or something? I don't know if it is clear in the picture, but the switch PCB and the rest of the panel were one single PCB until it broke.


1335924982 2887 FT0 Img392


For a picture of before, see the switch on the other side; the fan speed select:


1335925073 2887 FT0 Img389


In this case, the upper side of the groove does have a purpose, but the lower groove serves no purpose at all that I am aware of. What ya think?
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Dr. Slack
Wed May 02 2012, 07:12AM
Dr. Slack Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Two possible things spring to mind, other than cynical enhanced damage sensitivty.

It reduces the thermal conductivity between the islands of board and the main board. Are there any thermistors and heaters on the board that take part in temperature control, or that need to be isolated from hotter components on the main board? I've often seen board slotting to modify heat flow.

Are the islands intended to be broken out and connected by remote cables for a different version of the installation, perhaps with the rotary controls on a no-room-behind dash panel?
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Steve Conner
Wed May 02 2012, 08:25AM
Steve Conner Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
I smell health and safety, I bet they're designed to give way in a crash smile
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Nicko
Wed May 02 2012, 01:10PM
Nicko Registered Member #1334 Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Steve Conner wrote ...

I smell health and safety, I bet they're designed to give way in a crash smile
Either that, or its clever design

Consider, its a part that is obviously (de facto) prone to being knocked hard. Do you want the whole PCB or its binnacle to suffer damage and have to be replaced at significant cost, or do you make the mount "sacrificial" so it's easy to repair or replace that part?

I'm inclined to believe its a deliberate sacrificial design decision - either to protect people or the rest of the dash - a huge amount of thought goes into such seeming minutiae in car design.
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Tetris
Wed May 02 2012, 03:15PM
Tetris Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660
her girlfriend... O.o not that I am against lesbos or anything...

What is that anyways? You said its an airconditioning unit, but why is that part sticking out?
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Inducktion
Wed May 02 2012, 03:38PM
Inducktion Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068
It's the knob that controls the temperature/fan speed for the air conditioner unit..

And you really didn't need to point that out about "her girlfriend" :p

I feel that was kind of unnecessary.
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Mads Barnkob
Wed May 02 2012, 05:15PM
Mads Barnkob Registered Member #1403 Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Any further comment regarding sex, gender or orientations are kindly asked to be taken to private messages.
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genious 7
Wed May 02 2012, 05:25PM
genious 7 Registered Member #2887 Joined: Sat May 29 2010, 11:10PM
Location: Panama City, Panama
Posts: 107
@HighVoltageChick

A typo; my mistake

It reduces the thermal conductivity between the islands of board and the main board. Are there any thermistors and heaters on the board that take part in temperature control, or that need to be isolated from hotter components on the main board? I've often seen board slotting to modify heat flow.

Nope, no thermistors; its just the switch; nothing should generate considerable heat.


Consider, its a part that is obviously (de facto) prone to being knocked hard. Do you want the whole PCB or its binnacle to suffer damage and have to be replaced at significant cost, or do you make the mount "sacrificial" so it's easy to repair or replace that part?

Nope, she went to the store to get it fixed; they only replaced the whole panel. That's why I ended up with it.

I think the health & safety theory is the correct one, but I really dont know
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Conundrum
Thu May 03 2012, 07:03PM
Conundrum Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4062
Probably there to provide a conduit for the airbag.
Obviously having the circuit board explode in the user's face if the airbag goes off would cause serious injury, so the breakaway points stop this.

This sort of thing is common in cars, the centre of the steering column typically has little grooves cut on the back .
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Tetris
Fri May 04 2012, 03:30PM
Tetris Registered Member #4016 Joined: Thu Jul 21 2011, 01:52AM
Location: Gainesville, FL
Posts: 660
Inducktion wrote ...

It's the knob that controls the temperature/fan speed for the air conditioner unit..

And you really didn't need to point that out about "her girlfriend" :p

I feel that was kind of unnecessary.

Fan speed control? Heh, we have no fan speed control... oh wait... did I just realize that.... O_o wow I'm being a tube light again...
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