Hey I'm into a phase on my project ( Wiring ) that I have always always bumbled through, and could use a bit of advise. This is a 1931 Model A ( 12 Volts now) being built from the ground up. No existing wiring is present. First question) Is 16 gauge wire ok for things like: headlights, taillights, starter solenoid and switch, and model A mechanical horn? Second question) Is the brake light pressure switch to be wired as a ground interrupter/contact or with 12 volts p***ing through it? Third question) Is the horn ****on to be wired as a ground interrupter/contact or with 12 volts p***ing through it? Thanks in advance.
If you use the search function there are many threads devoted to wiring your project including wire sizing,length,etc. I'm sure you will find all the info you need and then some.
Break down and buy a wiring kit,Rebel wire is a fairly inexpensive kit and you will be miles ahead without pulling your hair out trying to figure how to make your harness and the gauge wires to use. HRP
1.) I like 14 gauge, even though it might be overkill - when crimping, there's just more wire to crimp. 2.) 12 volts p***es through pressure switch to brake lights 3.) horn ****on grounds horn
You might want to read this... http://www.jalopyjournal.com/forum/threads/wiring-101.843579/ I would consider #16 inadequate for headlights, rear lights, or horn; use a minimum of #14, preferably #12 for the headlights. The brake light switch should be wired as a 12V feed, not a grounding point. The horn switch, that will depend on what type of switch you're using. If you're using a steering wheel horn ****on/ring, these typically need to be wired as a grounding point. If you're using a ****on on the dash, then wire it as a 12V feed; that way you only need to run one wire to the horn, ground the other side of the horn at it's mount.
"]If you use the search function there are many threads devoted to wiring your project including wire sizing,length,etc. I'm sure you will find all the info you need and then some.[/QUOTE] First, I have searched a bunch and figured some things out. However these three questions have not been made clear to me, I would like some direct advise from Wiring experts please. Electrical Wiring Help Please. Second, The car came with a new Ron Francis wiring kit (from the late 1980s) and it only has 10 gauge and 16 gauge wire in it. The schematic actually is not clear about the "polarity" of the brake light and horn ****on. And I ask for advise because other searches have suggested using 12 and 14 gauge wire for the lion's share of the car. Who is right? The random search or the Ron Francis kit? Thus the confusion. Thus the questions.
I'm no expert but I have scratch made my own fuse panels & wiring before after market kits were available more than 40 years ago,one problem with this type of wiring is if there is a problem tracing wires becomes a problem,the aftermarket kits are clearly market where the go. In typical fashion,someone ask for help and then *****es about it. In the past ten years I have wire in excess of 20 cars,I was only offering some sage advice,btw,16 gauge is fine for a horn & brake lights but if it makes you feel better use 14 gauge. you can feel free to take it this with a grain of salt! HRP
Read the link I posted; this will fully explain how to calculate wire size/length for a given load. And this is why I'm not impressed with any aftermarket 'wiring kit' I've seen because they do generally do a 'one-size-fits-all' design (mostly for cost reasons) that won't be adequate for all circuits. One basic rule in electrical is too small is always bad, too big is good....
I wouldn't use a pressure switch for the brake lights. Brake fluid is flammable and when the switch leaks, as most inevitably do, it can start a fire. A switch on the pedal is a much better option. If you do use the pressure switch, connect it to a circuit that is only powered with the key on. Then you will be with the car if a fire starts.
Ron Francis kit's used to be ***igned a serial number. If your's has a s/n, contact RF, they will know what the unit was designed for, etc.
If you have an old harness kit that might be 30 years old, chuck it. Especially if it has no fuse panel. The stuff today is so much better. Rebel has a nice selection.
Better to be safe with a little larger wire if in doubt. Won't cost much. You can find the amp draw on everything and size the wire to match. Use a relay on the headlamps.
Sooo , searching didn't yield answers,,, First question) Is 16 gauge wire ok for things like: headlights, taillights, starter solenoid and switch, and model A mechanical horn? No, 16 gauge is not enough for some items of the list, yet for some items 16ga is fine. Second question) Is the brake light pressure switch to be wired as a ground interrupter/contact or with 12 volts p***ing through it? Because of the turnsignal wiring, the brake light switch needs to have 12 volts p*** thru it. Third question) Is the horn ****on to be wired as a ground interrupter/contact or with 12 volts p***ing through it? A horn ****on mounted in the center of the steering wheel on the column can only provide a ground. Generally its best to use that as a relay trigger for the horn & not the horn itself.
There's a book called "How to wire your street rod" that has some really basic and simple drawings to follow. Wire gages are shown too. Good reference if you are intending on doing it on your own and it's on an older vehicle with older engine, ignition and accessories. Be safe in this area for sure.
what ever happened to following Ohm's law? example headlamps on low bean put out say 40 watts. Watts divided by volts equals 3.5 amps times 2 for 2 lights circuit draws 7 Amps plus some for wire and connection resistance call it 9 or 10, Is 16 gauge wire sufficient for that draw? High beams 55 watts divided by 12 = call it 5 amps or 10 for both lamps, make it 12 for misc. resistance in the circuit. What gauge of wire is necessary for that load?
If you're using relays to control the high load stuff like headlights, horn and A/C clutch, the 16 gage would fine but only to trigger the relay. I like to use 12 gauge from relay to the load and 10 gage to power up the relays. If you're using turn signals, run 12 volts through the brake light switch but if not, I'd run the relay's ground to the brake switch to keep the load off it. Those switches are famous for a short life. I always use a pedal activated switch whenever possible. They won't need a relay unless you have 3 brake lights per side or a sequential 60s ford product setup...think T-bird or Cougar.
Thanks for the advice guys. Helped me over tat hurtle. The " how to wire a street rod" book might be a good investment. Ohm's law??? When I said "bumbled through" I meant it. I've never had any electrical mentors or even buddies. Wrenching, welding, machining, painting, fab, tuning, solid. When it comes to wiring, I am at square one.
Millions of vehicles have used a pressure type brake switch. Millions of vehicles have used mechanical brake switches. I have investigated fires caused by both switches (not including the Ford speed control switches). When wiring a car I use one gauge thicker wire then what is normally used. The kits I have used also follow this rule to some degree, though I have changed wires that I felt were too thin for that circuit.
I don't. Those are just numbers picked out out of the air to show how the math works. I believe typical non halogen tungstun filament US sealed headlamps were rated for 35 lo beam/55 high beam. Newer halogen lamps are rated a bit higher maybe 55/65. One would have to check out the specs with a little research. The point is that you can always determine the wire gauge requirements if you know the load that the circuit will draw, whether expressed as peak amp draw like a starter or heater fan, or in watts like lamps. And when in doubt, go thicker.
I dont know, Ive been working on cars for loke 40 plus years and I have never seen a car fire from a leaky pressure brake switch. If fire is your worry then you had never put gas in your car. Id be more worried about the fuel line coming off and causing a fire than a leaky switch. NOt to say it could never happen but Id bet on the Brooklyn Bridge falling on you first than that happening. Just converted my model a from 6 volts to 12 volts. Speedway has a great little book on that subject. It pointed out that actually when you go up in voltage your amps go down. This has to do with Ohms Law. I wont go into that here but great little book for a few dollars. when wiring ,when in doubt on size go up. you wont be disappointed. Also use fuses or circuit breakers in just about every circuit. Cheap insurance. OK thats my 2 cents worth.yruhot
I have wired vehicles from scratch building my own harness, and I have wired vehicles with after market harnesses. I have always used a company called EZwiring, they have good prices. I can say that after doing it both ways I will NEVER wire another from scratch! It is so much easier, cleaner, and cheaper to just buy a universal harness.
I try to avoid re-inventing the wheel. The kits take out most of the guess work right up front. I'll call myself a wiring expert once I power up the kit in my Ford and everything works!
I've wired my cars from scratch. The booklet HOW TO WIRE YOUR STREET ROD is very good. The info on GM column wiring was especially helpful. Would have taken me a while to figure that out. And, yes, use a horn relay.
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