9 ms·

Because cars are not expected, under normal circumstances, to experience abnormal amounts of current on any given circuit. Unlike a house, where you can easily

by x0054 12y ago

Because cars are not expected, under normal circumstances, to experience abnormal amounts of current on any given circuit. Unlike a house, where you can easily plug in something into the outlet that can overwhelm the circuit, in a car each circuit is designed specifically for a given maximum load. When you blow a circuit in a house, you have most likely massed up and plugged too many things into one outlet, or your device is drawing too much power. You learn from your mistake, unplug the device, and reset the circuit. If a car blows a circuit, then there is something seriously wrong with some component of the car or the wiring. You don't want the user to be able to reset the circuit, you want someone who knows what they are doing to figure our what went wrong. I fix all of my own cars, and never once have I ever had a blow fuse "just because." There always was an underlining cause which needed to be addressed. Except once, when a 10A fuse was used in a circuit that required a 25A fuse, on a window motor. So, basically, in a well functioning and well designed car a fuse will not fail just because. So why bother replacing a part that costs less then a cent with a part that costs several dollars. I hate this attitude, just because something CAN be complex, does NOT mean it has to be complex. Take car modules for instance. It used to be that back in the day (the 90s) your headlights were operated by a mechanical relay. This relay was expected to fail at some point (though they very rarely actually did fail) and as a result this relay was installed in an easily accessible place. If it did fail, it would cost $10-15 to replace it plus 5 minutes of labor. New cars nowadays have solid state switching modules to operate headlights, and everything else in your car. These components are not expected to fail, even though they often do. Don't believe me, talk to any mechanic. However, because they are not expected to fail, they are often installed deep inside the car. So, now, if your headlight module fails, it costs $400 in parts, and several hours of labor to fix the same problem. Progress? Stop making things needlessly complicated. Blade fuses are a fine solution to a problem.

moe 12y ago
Progress? Yes. For the companies selling the parts and the repair services.
brudgers 12y ago
The reason fuses are prohibited in distribution panels for homes and many other types of buildings has nothing to do with the magnitude of the potential overcurrents. The prohibitions on fuses and requirements for circuit breakers exist because experience has shown that occupants will frequently short across rather than replacing blown fuses. The resulting fire and shock hazard endanger not only the occupants but the general public and firefighters responding to calls.
- Spooky23 12y ago
  You got it. I looked at a fixer upper house where the mains still had an ancient fuse box. Most of the high draw fuses had old pennies wedged in with a blown fuse. How the place was standing, I don't know!
  - rbanffy 12y ago
    Well... In some extraordinary cases, shorting is the right thing to do. http://www.eetimes.com/author.asp?section_id=4&doc_id=1283891 http://www.eetimes.com/author.asp?section_id=4&doc_id=128389... But, still, you need someone who understands what't being done.
- chrisfarms 12y ago
  When I first moved into my flat I discovered that the previous owner had wedged some kind of brass plate across the contacts for the cooker circuit. Terrifying.
tzs 12y ago
> These components are not expected to fail, even though they often do. Don't believe me, talk to any mechanic. However, because they are not expected to fail, they are often installed deep inside the car. So, now, if your headlight module fails, it costs $400 in parts, and several hours of labor to fix the same problem. Progress? Hell, when the HEADLIGHT BULB fails, which is something that IS expected to happen, it can be a pain in the ass to deal with on some cars. Some have sealed headlight units that have to be replaced when a bulb dies, costing hundreds of dollars. Even ones where the bulb can be replaced sometimes make it ridiculously annoying. A low beam went out on my 2006 Honda CR-V. In theory it is easy to replace. Reach in, disconnect a cable, pull off a rubber seal, release a metal retaining clip, and the bulb can be pulled out. Reverse those steps with the new bulb, and you are done. In reality, there is a bunch of stuff in the way, making it very hard to actually reach the damn thing. On one side, I was only able to do it by wedging my arm in, leaving it bruised and very sore for days. At least I could actually reach the low beams. While there, I tried to reach the high beams and could not get anywhere near them--I think when they go out I'm just going to give up on them. Once you are in, it goes well, with the possible exception of the retaining clip. This is not unique to Honda, BTW. A lot of cars use the same kind of retaining clamp. Here's a drawing of how it works [1]. It is hinged at one end (the red circled part in that image), and it hooks under a piece of metal at the other end. It takes a fairly large force to make it hook there. Here's the problem. You can't see this damn thing when you are trying to unlatch or latch it. The headlight housing is in the way. You can maybe see the end of it that is toward the bottom, but that is not helpful because they orient it so the hinge is on the bottom, and it is not the hinge end that people have trouble with. Looking at YouTube videos of people explaining how to change headlight bulbs, and reading forums, it looks like it either latches easily, or it just won't latch and you are in for 30 minutes of flailing. All the car maker would have to do is flip the orientation 180 degrees, so that the hinge is on top and the latching part on the bottom. Then you could see the latching part, and it least know what you are trying to do. The way they are now, you are going in blind. I can understand that when they lay out components in the engine compartment, they have many constraints, so I can believe that all those things that made it hard for me to reach the bulb had to be there. I can believe that making an opening big enough for easy bulb changing might have made them have to make the car longer or something, that would have added a noticeable cost, and they could reasonably decide that it wasn't worth it. The retaining clip orientation, though, is almost certainly completely arbitrary, and they just did not consider the effect on the ease of bulb changing (or deliberately picked the worst orientation to encourage people to visit a dealer instead of changing their own bulb). [1] http://www.suzuki-forums.com/attachments/2g-2006-grand-vitara/9975d1277744431-broken-retainer-clip-headlamp-replacement-brokenpiece.png http://www.suzuki-forums.com/attachments/2g-2006-grand-vitar...
walshemj 12y ago
Yes I suspect that woz hasn't ever seen any serious electrical kit the fuses for those look just like the normal cartridge fuses but way scaled up. it was only 20 years ago that a local company stopped making knife edge switches (the sort used as props in Frankenstein movies )
grkvlt 12y ago
> This relay was expected to fail at some point (though they very rarely actually did fail) > These components are not expected to fail, even though they often do. I think this is wrong. If you look at QA statistics, you will find that parts are getting _more_ reliable. The old relays were expected to fail becuase they _did_ fail. The new modules are not expected to fail, and this is indeed the case. They fail much less often, and of course this means that in the occasional cases where failure occurs, it will be difficult to replace or repair. Overall reliability is increasing and to say otherwise would seem to be a glib misstatement or misunderstanding.

by x0054 12y ago

moe 12y ago

Progress? Yes. For the companies selling the parts and the repair services.

brudgers 12y ago

The reason fuses are prohibited in distribution panels for homes and many other types of buildings has nothing to do with the magnitude of the potential overcurrents. The prohibitions on fuses and requirements for circuit breakers exist because experience has shown that occupants will frequently short across rather than replacing blown fuses. The resulting fire and shock hazard endanger not only the occupants but the general public and firefighters responding to calls.

Spooky23 12y ago
You got it. I looked at a fixer upper house where the mains still had an ancient fuse box. Most of the high draw fuses had old pennies wedged in with a blown fuse. How the place was standing, I don't know!
- rbanffy 12y ago
  Well... In some extraordinary cases, shorting is the right thing to do. http://www.eetimes.com/author.asp?section_id=4&doc_id=1283891 http://www.eetimes.com/author.asp?section_id=4&doc_id=128389... But, still, you need someone who understands what't being done.
chrisfarms 12y ago
When I first moved into my flat I discovered that the previous owner had wedged some kind of brass plate across the contacts for the cooker circuit. Terrifying.

tzs 12y ago

> These components are not expected to fail, even though they often do. Don't believe me, talk to any mechanic. However, because they are not expected to fail, they are often installed deep inside the car. So, now, if your headlight module fails, it costs $400 in parts, and several hours of labor to fix the same problem. Progress? Hell, when the HEADLIGHT BULB fails, which is something that IS expected to happen, it can be a pain in the ass to deal with on some cars. Some have sealed headlight units that have to be replaced when a bulb dies, costing hundreds of dollars. Even ones where the bulb can be replaced sometimes make it ridiculously annoying. A low beam went out on my 2006 Honda CR-V. In theory it is easy to replace. Reach in, disconnect a cable, pull off a rubber seal, release a metal retaining clip, and the bulb can be pulled out. Reverse those steps with the new bulb, and you are done. In reality, there is a bunch of stuff in the way, making it very hard to actually reach the damn thing. On one side, I was only able to do it by wedging my arm in, leaving it bruised and very sore for days. At least I could actually reach the low beams. While there, I tried to reach the high beams and could not get anywhere near them--I think when they go out I'm just going to give up on them. Once you are in, it goes well, with the possible exception of the retaining clip. This is not unique to Honda, BTW. A lot of cars use the same kind of retaining clamp. Here's a drawing of how it works [1]. It is hinged at one end (the red circled part in that image), and it hooks under a piece of metal at the other end. It takes a fairly large force to make it hook there. Here's the problem. You can't see this damn thing when you are trying to unlatch or latch it. The headlight housing is in the way. You can maybe see the end of it that is toward the bottom, but that is not helpful because they orient it so the hinge is on the bottom, and it is not the hinge end that people have trouble with. Looking at YouTube videos of people explaining how to change headlight bulbs, and reading forums, it looks like it either latches easily, or it just won't latch and you are in for 30 minutes of flailing. All the car maker would have to do is flip the orientation 180 degrees, so that the hinge is on top and the latching part on the bottom. Then you could see the latching part, and it least know what you are trying to do. The way they are now, you are going in blind. I can understand that when they lay out components in the engine compartment, they have many constraints, so I can believe that all those things that made it hard for me to reach the bulb had to be there. I can believe that making an opening big enough for easy bulb changing might have made them have to make the car longer or something, that would have added a noticeable cost, and they could reasonably decide that it wasn't worth it. The retaining clip orientation, though, is almost certainly completely arbitrary, and they just did not consider the effect on the ease of bulb changing (or deliberately picked the worst orientation to encourage people to visit a dealer instead of changing their own bulb). [1] http://www.suzuki-forums.com/attachments/2g-2006-grand-vitara/9975d1277744431-broken-retainer-clip-headlamp-replacement-brokenpiece.png http://www.suzuki-forums.com/attachments/2g-2006-grand-vitar...

walshemj 12y ago

Yes I suspect that woz hasn't ever seen any serious electrical kit the fuses for those look just like the normal cartridge fuses but way scaled up. it was only 20 years ago that a local company stopped making knife edge switches (the sort used as props in Frankenstein movies )

grkvlt 12y ago

> This relay was expected to fail at some point (though they very rarely actually did fail) > These components are not expected to fail, even though they often do. I think this is wrong. If you look at QA statistics, you will find that parts are getting _more_ reliable. The old relays were expected to fail becuase they _did_ fail. The new modules are not expected to fail, and this is indeed the case. They fail much less often, and of course this means that in the occasional cases where failure occurs, it will be difficult to replace or repair. Overall reliability is increasing and to say otherwise would seem to be a glib misstatement or misunderstanding.