Why does a 6Volt system use the size wire it uses and a 12 Volt that has TWICE the volts uses a smaller size wire without overloading the smaller size wire?
Most automotive (actually, most any electrical) items use roughly the same amount of power in watts to perform their functions (given the same function) regardless of voltage. As an example, a 24 watt lamp will use 2 amps at 12 volts. Drop the voltage to 6, now it uses 4 amps. Watts is volts times amps, so the higher the voltage, the lower the amps. Wire is sized by amps, so more amps needs bigger wire. Voltage affects insulation type; as volts go up, better insulation is needed. Below about 600 volts, most insulation is selected for its mechanical properties; how well it stays flexible, resists abrasion, etc. Pretty much any non-conducting material will work. Go higher, and the dielectric properties become more important. At a high enough voltage, almost any material will conduct electricity.
Bob, it may be helpful to think about electronics like you would with hydraulics, just as an analogy (keeping in mind that at some point all analogies break down). So if we go with that, then volts = pressure, amps = flow, & watts = power (flow x pressure). If the power need remains the same, and pressure goes up, then flow has to come down. With reduced flow you don't need as big a pipe, right? Or look at it the other way around. You have the same power needs, but pressure is cut in half, so you need a twice as much flow, right? Well then you need a bigger pipe. To make it even simpler, think about a garden hose. Your trying to hose down the driveway and you've hit a spot of dirt that won't budge. You can either crank up the pressure, by putting your thumb over it; or you can crank up the flow. If the hose is too small & you can't get enough flow out of it, you need to use a bigger hose. Make sense? The 12 volt system doesn't need as large of wire (pipe/hose), cause it doesn't need as much amps (flow), it gets the job done with more voltage (pressure). The 6 volt system doesn't have as much voltage (pressure) so it needs more amps (flow) to get the job done. So it needs a bigger wire (pipe/hose) to handle the amps (flow). Just trying to supply a mental image that might help it make sense. Having worked with hydraulics and electronics for many years, I've often found it helpful to look at electronics this way.
Picked this up today for a buck, is it worth reading, or has someone posted the corrections some were? Bob
I'm sure it's worth reading for any novice; the one thing I'd take with a grain of salt is any directions for sizing wire/components as it's industry standard to 'undersize' things to save money. And the aftermarket is just as, if not more, guilty of doing this. Automotive electrical is the only part of the electrical industry that has NO 'safety authority' overseeing it...
I agree with Steve. When rewiring my '50 Buick I used next size larger in almost , if not all, cases. This for six volt. Now with twelve volt, wiring is plenty big enough. Ben Ben
So, if I don't care to "save" money can I wire a 12 volt system with 6 volt size wire? It sure as hell looks a lot nicer. Bob
The thing to remember is there's no such thing as '12 volt' and '6 volt' wire, it's just wire. You use different sizes for different loads is all. Now it's true that 6 volt loads will generally be twice as large than the 'same' load on 12 volts, but that doesn't necessarily mean that you double the wire size as wire ampacity doesn't go up linearly with size; you still need to calculate the load.
Steve, What are you using for the flasher mount/wiring? I find lots of relay mounts, but not any for flashers. Thanks Doug
Thanks, I had forgotten on the headlight pigtail. Still would like to have one that I could mount (screw, etc) to a base plate.
A flasher will fit in a regular 5 pin relay socket, some of which have mounting provisions, either linked or individually. Top row will hold three Bosch relays and two flashers. Need to work on my '47, panel is sure getting dusty.
Hey how about this one...Cole Hersee. http://www.allbatterysalesandservice.com/browse.cfm/4,2984.html
Steve: You may not remember, but you really helped me rewire my roadster pickup a couple of years ago...(installed a '40 dash and new gauges, new wiring)......... AND, now, am starting to wire my latest project. I have questions about wiring in a GM 3-wire alternator. Can you PM me so that we can chat about my tasks that lay ahead. I really admire your knowledge and ability to explain how this electrical magic works. Thanks Russ Verbael Yuma, Arizona
Keeping electrical questions on a one to one basis with someone you think understands it saves all the second, third and whatever contradicting opinions. No two people will give you like answers to the most basic electrical question. It is a gift given at birth, it can't be explained. Bob
Steve you don't like soldering ?, I use that on the race cars ,thinking it would hold up to vibration better.
Howzabout crimp and solder? Redundancy man, that's what put us on the moon (or a sound stage in new Mexico, whatever you believe.)
GM three wire alternators are all I'll use, Cheap to buy, reliable and easy to wire, the large terminal is ten gauge wire, goes to the starter where the positive cable is, on the two prong plug, the white wire (smaller of the two on the plug), goes to the acc side of the ignition switch, the remaining red wire on the plug can be wired two ways, either is correct, loop it onto the large terminal of the alternator, or as I do, to a battery terminal on the fuse box. The white wire sends current from the ign switch telling the alternator it's time to start charging when the key is in the run position, after the engine starts, the same wire now carries current to the switch, and will allow the engine to keep running after the key is switched off, unless it's wired to the acc post. The red wire on the plug, tells the regulator how much to charge based on battery voltage, or on a car with it attached to the fuse panel, it'll tell the alternator how much current the car requires while it's running. Clear as mud?
^^^^^^^^ That's a First! Nobody ever took the time to explain what the wires do, thanks for taking the time to post that. Bob
I just like to see how others solve problems and pick up on any tips like components, terminals and crimpers. I promise not to interrupt with my lame ass way of doing something. I taught H.S. Autoshop starting in 1970 and retired in 2010. (with a few interruptions). The biggest challenge was getting the light bulb over each student's head to come on when they 'got it'. The biggest change over those years is that today's kids are willing to accept that something 'just works'. If not then replace it. With solid state devices and 'computers', in many cases that is the correct solution. The problems start when putting in a new one doesn't fix the original issue. Oh, the stories I could tell. But I digress.
THANKS for the lesson...very easy to understand. I needed this to wire in the alternator on my sectioned shoebox.
This is the Kwik Wire manual that came with my harness, but it shows a lot of excellent basic wiring. I'm also big on GM 3-wire alternators, very straight forward to hook up. http://kwikwire.com/content/Kwik Wire - Instruction Book.pdf
any info on the correct amperage fuse for: -70s Ford dash gauge volt limiter running 2 things: a gas gauge, a temp gauge, .....and an added SW voltmeter that is not going through the limiter . Nothing else on this circuit. The 2 gauges and limiter are early 70s Ford pickup.
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