Do you have to wire it through the alt or can you pick up another 12 volt battery source like cigar lighter.Hate to run that big alt wire inside and back out Thanks
last I knew it had to be in series not parallel with the circuit and needed to be in the primary charging circuit and in most cases would have a 10 ga. wire running thru it. Polarity matters as the ga. will or can work backwards. I never use them anymore and go with a voltmeter which can be tagged to any battery supply circuit with a 16 ga wire.
Yes, if you want to use an amp meter, you have to run the big alt wire. Amps are the quantity of electricity. Think of them like gallons of water. If you wanted to measure how many gallons of water are coming out of your garden hose, you'd put the end of it in a bucket. The bucket is like the amp meter. They both measure quantity. You can't pick up another battery source from somewhere else because it's like putting a Y on your faucet and adding a second garden hose. The second garden hose isn't going to measure any of the water going through the first garden hose. That's why you have to run the big wire if you use an amp meter. Sent from my iPhone using H.A.M.B.
Amps are like he said: flow rate (buckets per minute), volts are like pressure difference. Like how hard it is to hold your thumb over the end of the hose. The more the pressure, the more the flow. There should not be any problem with running a big wire through that little loop on your ammeter just use about a 3/8 OD welding cable and fuse both ends of the wire just in case. No offense to that prior poster but the correct term is ammeter not amp meter.
No you only pick up the amperage that actually going into the battery the rest of that hundred amp is going to other stuff before it ever gets to the battery so unless the battery is very low on charge the amount of current going to the battery is fairly small. Controlled by voltage difference. 100 amp alternator doesn't put out a hundred amps all the time it only puts out enough to power everything on the car Plus keep the battery charged
Great and correct theory. The problem comes when the battery is almost dead and you (or someone else) starts the car with none of the accessories turned on. I don't think I would like to do that to my amp gauge. Charlie Stephens
Still won't hurt the ammeter as it is only measuring the inductive field going down the wire. Which is fairly weak and all it may do is Peg out the ammeter against its own little internal Springs. It's not like a speedometer that gets some junk between the magnets and rips off the needle.
When the AMMETER being used has two (2) posts, you are actually wiring a less that 30 amp 'coupler' in series with the main stream. Run some accessories and you are 'daring' the obvious to happen. IF a 'loop' type ammeter is available, it is merely an 'observer', NOT a 'fuse' with a face. I have replaced a few ammeters in Panteras that died on the freeway, DEAD Voltage, nothing works... Yeah. A 'fuse'...LOL I saw a diagram on the use of a 'shunt' in use with a S/W two post ammeter, but I simply use a Volt meter. No longer insistent on the 'tradition' of the gauge matching the set...Most gauge mfrs also make a matching Volt meter. "But I ran an ammeter for years with no problems..." Good. Just carry a short 12 gauge jumper with alligator clips. And make sure you can reach behind easily.
That's semi-true if you have a true inductive ammeter (no actual physical connection of the wire) but patently untrue if using most aftermarket ammeters where the wire connects to the meter. Put a 100+ amps through a 30 or 60 amp meter and you'll let the smoke out.... Even with an inductive meter, excess current can damage the meter movement under the right conditions.
Not to mention running your 100 amps of charging power in through the dash and back out again. A chaffed wire has been the cause of more than one car fire!
I'll just get rid of amp and go the volt meter.I didn't want to run the alt wire inside of car as it is a 1 wire and 100amp. was going to run it through the cigar lighter and back to the 12 volt straight from battery.Thanks
So what would happen if you wired a car WITHOUT an Ammeter or Voltmeter, is the chance of a fire less? Bob
Stictly speaking, the fewer items and/or circuits, the less chance of electrical issues. I figure you are kidding around, Bob, so I had to throw that out there
Theoretically, Yes. In fact no wires will drop the chances even lower. Sent from my XT1650 using H.A.M.B. mobile app
No, That was an honest question from someone that is clueless to all things electrical. I do read just about every wiring/electrical post on the HAMB, and sort of understand the first reply, then the next reply comes in and contradicts the first one and I continue to know less with every reading. I find my joy in rust repair and body work, stuff you can see and understand. Bob
Ammeters carry a lot of current unnecessarily through the firewall and dash increasing the chances of a short that could cause a fire. Volt meters are not the same type of problem as they do not carry much amperage. Sent from my XT1650 using H.A.M.B. mobile app
Well, that gives us a couple things in common, Bob. I too, am a bodyman first, and an electrician, last. I have to say yes, running without an ammmeter or a voltmeter would decrease the chances of an electrical fire, but taking care in wire routing would minimize those chances, along with using quality ammeters. I have a really nice Mercury here that had a wiring fire behind the dash 10 years ago, and I am still struggling to get it rewired to my satisfaction. Meaning getting it to the point I am not scared to hook a battery up to it.
Current, amperes, is the flow of electrons, think of it as gallons per minute in water flow. Voltage, volts, is the pressure that forces the electrons to flow - just like pressure forces water to flow. A amp meter that has thick wires leading ALOT of current (all the generator produces, and potentially everything the battery can put out) has the potential to unleash a huge amount of energy, in case of a short circuit. Just to put it in proportion, I'm guessing most of you in here weld a little? You have an idea how much heat 100 or 200A of welding current creates? The welder probably has double or triple the voltage compared to the car battery, but the battery can usually supply 500-1000A - and there's probably no fuses protecting the ammeter wiring in your car. How's that for a fire hazard? A voltage gauge only "senses the pressure" in the circuit. It is (usually) connected by a thin wire, through a fuse that will blow before the thin wire is overloaded - say, at 10A or less. At that low current there isn't alot of energy available, and there is little risk of problems that create any serious amount of heat - if there's a short circuit or overload the fuse is blown and that's that.
It's extremely hard to properly fuse charging system wiring. Here's why.... First, the fuse has to be rated for the maximum output of the system. If you have a 100 amp alternator, you need a 125 amp fuse; remember that a fuse can't be run at it's max rating or you'll suffer nuisance tripping. So adding 25% gives you the 'cushion' you need to avoid that. Second, what size wire are you using from the alternator to the battery? Or to the ammeter? The typical #8 or 6 wire is rated for 1/2 or less of a 125 amp fuse. If you have a catastrophic short, the fuse will blow. But what if you have a partial short? The big fuse will allow that to sizzle away and you may have a pretty good fire going before it blows, if it does. This is where fusible links come it. A fusible link will withstand short-term overload without tripping, but will melt (open) before actual wire damage occurs... IF it's sized correctly. That's the catch; I haven't been able to find any slope graphs that show the time/current relationship for proper sizing. For best protection, using a link rated for the actual wire size would be best, but that may produce occasional nuisance tripping if the available current is too far above the wire rating. The OEMs never fused these circuits with conventional fuses, on the rare occasions when they did supply overcurrent protection they used fusible links. This is just one of the reasons ammeters fell out of favor.
Automotive ammeters are just voltmeters with a low resistance device inside called a shunt that carries all of the current to be measured. As current moves across the very low resistance a very small voltage drop proportional to the amount of current flow occurs. The voltmeter measures this voltage and displays it on a scale calibrated in Amps. If you wanted to run a "safe" ammeter, the best solution would be a meter with an external shunt that could be mounted in the engine compartment. Two small gauge wires from the shunt would then power the ammeter in the car. VDO makes a meter that uses an external shunt. This completes todays lesson.
Back in the 70's amp meters were causing A LOT of fires in mopars probably one of the first mandated recalls of the automotive world. replaced a bunch. Volt meter will tell you about the same info and more with less fire worry.
Ok, Using the "it's just like water in a hose" analogy what difference does it make if you measure amps or volts? Are all systems getting the same flow or pressure? Why do you want to know what one or the other are doing as long as the lawn gets watered? Using water to explain fire never made sense to me in the first place. Lave flow maybe. Bob
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