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46 votes
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Why don't cars have circuit breakers instead of fuses?

(1) Fuses are cheap. Really cheap. You can get a variety pack of 100 for $8 or so. Circuit breakers for 12V systems are available, but are not cheap (more like $10 each). My car has 40 or 50 circuits, ...
Jon Custer's user avatar
14 votes

Why don't cars have circuit breakers instead of fuses?

I don't have a definitive answer, but believe it is a combination of factors and boils down to the following: Cost: While both do the job of protecting circuits, a fuse runs you cents per unit, while ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
11 votes

Are mechanical relays still used for turn signal circuits? If not, where does the clicking noise come from?

In my car the indicators are controlled with solid state electronics and so could switch silently as there is no relay or bi-metallic strip contactor to make a noise as they are activated. There is ...
uɐɪ's user avatar
  • 253
9 votes
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Reliable 12V supply in car

When properly installing an amplifier a large gauge wire is run from the battery to trunk area. A fuse is installed as close to the battery as possible. The amplifier then connects to that wire. If ...
vini_i's user avatar
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8 votes

Why don't cars have circuit breakers instead of fuses?

In addition to the other good answers: You'll see self-resetting circuit breakers in heavy-truck applications, which is a far more abusive environment, and prone to intermittent faults (esp. in ...
GB540's user avatar
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7 votes
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Simplest installation of car-powered car-pc

Most everything external of the ECU is going to be 12vdc (+/-2v). (NOTE: As @juhist points out, more and more cars are supporting 5vdc output to charge handheld devices through USB ports. 5vdc may ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
7 votes

Control Systems of Modern Engines

Another way to go would be to check out Speeduino. It's an open source DIY ECU. The software is freely available here: https://github.com/noisymime/speeduino/ and it can run on an Arduino. If there's ...
Richard's user avatar
  • 196
7 votes
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Battery Relocation to Trunk Pros & Cons?

I think you have most of the stuff covered as far as pros/cons. The "main" reason people do this is weight distribution, as you stated. This is for the performance to place more weight in ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
6 votes

Fixing a water-damaged remote key

I accidentally ran the smart key for my '09 Jaguar XF supercharged sedan through the washing machine once. It was submerged in water for about 10 minutes until I found it. I was able to fix it by ...
Antwine Barfield's user avatar
6 votes
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Tapping into the on-board computer

You cannot easily "tap" into any ECU/PCM. Depending on what year your vehicle is, it could be a simple set of analog gauges which you could tap into the signal line, but you'll need to do some ...
DustinDavis's user avatar
6 votes

what sensors and formula are used to control VGT/VNT turbos?

Dodge installed VNT Turbochargers on cars in 89 and 90. The most well known of which is the 1989 Shelby CSX-VNT. The vanes were controlled by a dual port vacuum actuator. There was nothing ...
rpmerf's user avatar
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6 votes

What happens if I disconnect the battery while the car is running?

When a Battery is disconnected from a running engine, there is a milliseconds high voltage spike that occurs the instant the terminal leaves the battery connector. Some researchers say it can be as ...
Robert Smith's user avatar
6 votes
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Why did the old-school thermal flashers remain in use for so long?

Three major reasons why they were used so long: 1. Cost - Even today a thermal flasher units cost about $2-2.50. The cheapest equivalent electronic flasher unit, which happens to be a direct ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
6 votes

cigarette lighter is always on

This behavior is by design and it was the same on pretty much any Ford of that era (at least it was on the Mondeo, Fiesta, Fusion and Focus IME) You can modify it to come on with the ignition but not ...
motosubatsu's user avatar
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5 votes
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Which electrical parts in motorcycles are obligatory for basic driving capacity?

Generally manufacturers aren't going to waste money on unnecessary components. You've got electrical components to: provide spark to the engine. an on/ off / kill switch to control engine on or ...
zipzit's user avatar
  • 6,539
5 votes

Tapping into the on-board computer

If your car has a OBD2/ODBII port then it is achievable. I'd imaging the simplest way would be to use a ELM327 type cable or even a bluetooth adapter to provide the interface between the pi and the ...
tallpaul's user avatar
  • 341
5 votes
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What happens if I disconnect the battery while the car is running?

Removing the battery with the car running is a bad idea. Rather than re-writing something which exists on the interwebz, I pulled this from Troubleshooters.com under the section called Automotive ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
5 votes

What happens if I disconnect the battery while the car is running?

If the car has electronic components, like ECUs, central commanding modules, etc, doing that "may" fry them...or not. Sometimes the ECU turns off the engine if the battery is non present. Same reason ...
Aram Alvarez's user avatar
  • 3,346
5 votes

What's wrong with using domestic flex cable for automotive purposes?

Automotive cables are normed (ISO 6722 ?). The insulation of automotive cables offer a superior resistance to heat, cold, chemicals and vibration. A common FLYR-cable should guarantee its insulation ...
Martin's user avatar
  • 8,458
5 votes

Are mechanical relays still used for turn signal circuits? If not, where does the clicking noise come from?

In the old days, the flasher used to be controlled by a little device that contained a bimetallic strip. When current was supplied to the flasher lamps, the strip would heat up, bend and turn off the ...
HandyHowie's user avatar
  • 25.4k
5 votes
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Should ground wires be fused?

I have fitted many accessories to cars, trucks and agricultural vehicles, some taking less than 1 amp and others several hundred or more. I have never put fuses on the earth or ground side. If the ...
Solar Mike's user avatar
  • 34.6k
5 votes

Control Systems of Modern Engines

Yes, do some research about early fuel injection systems and electronic ignition. You will find Bosch had some superb info about how they worked etc with really good diagrams and detailed explanations....
Solar Mike's user avatar
  • 34.6k
4 votes

What voltage does the ECU need?

If you're talking about a regular 12V battery vehicle, then the ECU is likely to work from 7V until 14V with no problem. That's the usual requirement for this kind of component.
PDuarte's user avatar
  • 217
4 votes

What happens if I disconnect the battery while the car is running?

The answer is a bit complex here: As Paulster2 has mentioned, the battery does help protect from transients, but as the alternator has its own regulator and the computer and audio system have their ...
Thomas's user avatar
  • 708
4 votes
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Defender Right Indicator Incorrectly Canceling while Turning Right

Troubleshooting: Pull out the rubber seal between the indicator stalk and the housing for the steering column and stalks. If this fixes the problem that means that the rubber is pulling down the ...
Harry Beadle's user avatar
4 votes

Why did the old-school thermal flashers remain in use for so long?

At the time your mg was originally made, the thermal flasher unit was cheap and effective. The use of electronics in most cars came along later, such as electronic ignition only became common place in ...
Solar Mike's user avatar
  • 34.6k
4 votes

How could a battery issue lead failures in ABS, Cruise control, stop-start, etc?

Some electronics are very susceptible to power differences. Most need continuous power in the ~12-14vdc range to function correctly. The starter, on the other hand, will work at lower voltage levels, ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
4 votes
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Question about cigarette lighter voltages/currents

It depends on the efficiency of the electronics inside the charger. Presumably it will be some kind of switching regulator that will be fairly efficient. Your calculations are correct for 100% ...
HandyHowie's user avatar
  • 25.4k
4 votes

Why don't cars have circuit breakers instead of fuses?

With one notable exception, automotive fuses almost never blow in the absence of a catastrophic failure such as a crash which causes wiring to be severed. One of the primary purposes of the fuses is ...
supercat's user avatar
  • 291
4 votes

Confused as to how components are powered

If you think about it, the electricity is available at the wall socket, but technically, the power doesn't come from there. It is routed to the wall socket via wiring. A vehicle is no different. Power ...
Pᴀᴜʟsᴛᴇʀ2's user avatar

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