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“Why does a car like the Tesla still have old-style fuses?”

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Re: “Why does a car like the Tesla still have old-style fuses?”

#41
post #33

Earlier quoted context omitted.

Australian plugs are good, but have the live pins at the top (so for example a dropped coin will balance across them and short when the plug is pulled out), the plug doesn’t have its own fuse and the socket isn’t shuttered with no plug inserted.

A few years ago they mandated the inner-most 5mm or so of the active pins be insulated for that reason, so that by the time you have enough of the plug out to reach exposed conductor with your fingers it's disconnected. At least that's idea... and I can't tell you how much ebay junk is sold with the old "illegal" exposed active pins

To be fair that wasn’t in the original design for the UK plugs either, sleeves were introduced in 1984.

Re: “Why does a car like the Tesla still have old-style fuses?”

#42
post #25

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 d…

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…

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!

Re: “Why does a car like the Tesla still have old-style fuses?”

#43
post #25

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 d…

> 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-vitar...

Re: “Why does a car like the Tesla still have old-style fuses?”

#44
Can't say I've ever seen a fuse in a car blow that didn't come from a short that had to be fixed anyway. Having a circuit breaker or software solution some end user would just flip again would damage the system even more and risk fires. Maybe Woz is smart about computers, but doesn't know anything about cars?

Re: “Why does a car like the Tesla still have old-style fuses?”

#45
post #25

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 d…

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…

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.

Re: “Why does a car like the Tesla still have old-style fuses?”

#46
post #25

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 d…

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 )

Re: “Why does a car like the Tesla still have old-style fuses?”

#47

Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically) I think WOZ is suggesting an active current control that, while doable, is probably too risky (and you really don't want to blow the expensive parts)

> Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically)

If you have something drawing too much current in a plane, and so it is a fire risk, it still might be overall safer to continue to use it. For instance, if it is something involved in lowering the landing gear you might decide it is safer to risk a small fire in order to get the gear down than to do a gear up landing. Something resettable, like a circuit breaker, therefore makes a lot of sense in a plane.

With a car you are almost never in that kind of situation.

Re: “Why does a car like the Tesla still have old-style fuses?”

#48
post #47

Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically) I think WOZ is suggesting an active current control that, while doable, is probably too risky (and you really don't want to blow the expensive parts)

> Well, even planes use CB today instead of fuses (and remote CBs on top of that, meaning they can be turned on/off electronically) If you have something drawing too much current in a plane, and so it is a fire risk, it still might be overall safer to continue to use it. For instance, if it is something involved in lowering the landing gear you might decide it is safer to risk a small fire in order to get the gear do…

You may also want/need to turn some things off, not necessarily because of a short-circuit.

Re: “Why does a car like the Tesla still have old-style fuses?”

#49

"What's the problem?" "Car won't start." "Did you try restarting it?"

No joke, I have seen a car which would occasionally refuse to start (with no indication of an error: the dash was basically blank) until you disconnected the battery, waited a few minutes, and then reconnected it.

Re: “Why does a car like the Tesla still have old-style fuses?”

#50
post #27

Earlier quoted context omitted.

On the point about building wiring codes, here in the UK we actually do have both central fuses/circuit-breakers and load specific fuses in the plug for each device. After reading your comment it did make me wonder as I plugged our coffee machine this morning how the design substantial chunk of plastic and metal I was holding was influenced by the aftermath of WW2.

The British plug is a marvel of good engineering. Other countries look on it with envy (except possibly Australia, which has a similar design of its own, IIRC). Now of course it was "overengineered" by the standards of the time, to compensate for our ludicrous, dangerous, and still-legally-required "ring main" system, which as you say was due to aftermath-of-WW2 copper shortages. But the plug design is the part we go…

Ring final circuits aren't legally required, you can use exclusively radials if you prefer. The cost is of course thicker cables for the same power rating, and so in most domestic installs it is still more economical to use ring circuits.

What makes you think ring circuits are dangerous? Incompetent installation?

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