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Automotive circuit breakers

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cranky108

cranky108

Electrical
Jul 23, 2007
6,293
In my car the auxiliary power plugs (12V) work when I plug in a camera, or a GPS, but when I plug in with a splitter (I have tried two so far), both, the plug fails. I have found the same thing when I plug in a mini-fridge. I found this on both plugs (front and rear).
Is there some sore of limiter, or maybe a circuit breaker going bad? That's the best I can figure out, without a total tearing apart the car.
Do car circuit breakers fail that way?

My older cars has fuses, and I have never had this issue before.
I had this issue with a car headlight switch once, which is why I am thinking this way.
 
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I would expect a fuse rather than a breaker. I think for fuses it's normally 10 amps for the old-style fire-starter cigarette lighter plug, but I don't know if a breaker would have the same nowadays. I expect the owners manual will tell what the capacity is.

It doesn't sound like a failure, just that you are exceeding what the circuit is supposed to deliver by driving too much with the splitter.
 
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What do you mean by the "plug fails"? Is it burning up or failing to supply power?
 
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If by "fail" you mean the circuit power is cut off, but it returns again if you remove some load, then that means it ALREADY has an auto-reset circuit breaker, which is becoming common on what are not called "accessory outlets" (because cigarettes are verbotten). If the outlet dies and does NOT come back, then you have a fuse. If you WANT to replace the fuse with an auto-reset circuit breaker, Bussman sells them, they are in the same format as the fuses, so you remove the fuse and plug it in it's place.

But... if you are plugging more devices in than the circuit can handle, then the REAL solution is to stop doing that...


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden
 
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My ‘90’s era GM’s had metal can circuit breakers for the electric windows mounted in sockets in fuse panel. I can not recall whether the lighter socket was protected by a fuse or a circuit breaker.
 
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You're an electrical engineer and you're asking these sort of really basic questions??

Seriously?

RTFM time I think.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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I am not an automotive engineer, I am a power engineer (as in above 100 kV).
I don't think I am overloading the "accessory outlets", and the two seem to act independent, so not on the same circuit.

Besides, I don't have a circuit diagram for this car, and the circuit diagrams I have seen for cars, are typically wrong anyway. It is a 2007 FORD, so beyond what I worked on in Highschool, and seems so computer centric.
Besides the typical diagram should look like battery-circuit breaker-outlet, but maybe there is something I am missing?

I'm still suspecting the circuit breaker might be going bad. I had hoped someone had seen this before, and knew for sure.



 
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Find a Ford forum for your vehicle. Somewhere there will know.
 
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On an F-150, because knowing what the vehicle is never provides a clue - says a 20 amp fuse that controls two outlets - front and rear and another 20 amp fuse for a lighter and the ODBII connection.

Of course, that's the as-built design. Not one where there's some other item vampired onto a wire under the vehicle that is now corroded into a high-resistance short circuit to the body somewhere. I watcn that South Main Garage and, while the vehicles that come in are certainly ones with problems, the sort of designs that are used that beg for corrosion and intermittent electrical failures is astounding. Ohh - the under-hood fuse box has a cover - but it's open to salt spray on the back. Great job.
 
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Auto design/manufacture is partly about cost points and compactness; you'll not likely find a 20A breaker in the size of a 20A fuse, which is also cheaper and has no moving parts. My car's fuse panel has around 30 fuses in a very compact package.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! faq731-376 forum1529 Entire Forum list
 
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I still don't understand what the problem is, from the description, but could it be that the fuse inside the the splitter plug is blowing? It is not obvious, but many of these come with like a 5 Amp fuse inside the spring-loaded pin that plugs into the power outlet.
 
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Cranky108,

The issue here is that you're being very vague about the symptoms and not providing any technical info or what fault finding you've tried.

So:
Do the power sockets work for your low power equipment AFTER you tried with the splitter and the fridge?
What did the spliiter have connected to it?
What do you mean by the "plug failed"?? This is unclear
What current draw does your fridge take at 12V?
Was the ignition on?
Was the engine running?

What model of 2007 Ford??

Aux sockets appear to be capable of anywhere from 10 to 20 A depending mainly on the fuse rating.
Also some aux socket fuses work other things as well so not all the 20A will be available
12V plugs can be difficult to get a good connection sometimes - the cheap ones split or are a little bit too big or small to fit in.
Did you try moving it around a bit and really pressing it home?
Does the splitter have a separate fuse?
Is the splitter faulty?
What does the manual say about the accessory / cig lighter sockets?


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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The fridge is not low power. The camera, and GPS are, as they use usb power cables. Last the splitter had the GPS and the camera, until it stopped working. The plug failed to output power (quit working).
I was driving while trying to figure out what was happening, so it was not like I could take a voltmeter under the hood.
It is a FORD Escape (not the car I wanted, but given the choices when my prior truck quit working). It seems to work well for driving, but with a few annoying issues.
I did try moving the plug a bit, but it did not seem to help.
Yes most splitters have a fuse just behind the positive connector. I would think it should not be faulty, as I had just removed it from the packaging, when the other one I had did not work.

I haven't reviewed the manual, as most of them are very general in nature, and don't have much trouble shooting guidance for these sort of smaller things.

The hard part is that all of the things I use work for a short time, then quit, which is why I believe it is a weak circuit breaker. The mini fridge I understand as it is a big current draw (I understand, but don't like), but the other are very small.

I use the camera on a daily commute with no problems, but adding the GPS and the power failing is the confusing part.
 
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What exactly do you mean by a "splitter"? Just two other 12V connectors or 2 USB connections?

Can you post a picture?

Those 12V USB power units are notorious for being very flaky, especially if you leave them in without connecting them or leave them in for a long time as there is nowhere for the heat to go so they overheat.

I think you need to have a normal 12V power connector with two wires and then measure the voltage. Or buy something like this
I've not come across a circuit breaker in a car of that age for powering the 12V accessory socket. I suspect your splitter is the issue.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
 
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Yeah - where are the burr covered sheet metal edges that you have to force your hand past if you want to avoid removing the entire interior of the car to gain access to remove the dash to get to a connector that was installed while the dash was on a bench?
 
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Probably a special place reserved in hell for automotive engineers. I can see one of them replacing an uunder-dash fuse for eternity while struggling to keep the A/C running.

Keith Cress
kcress -
 
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