In my time as a tradesman over the last 15 years, i have had the pleasure of working on quite a few hot rods and street rods and the all seem to have very similar issues. The wiring woes! I am dual qualed in mechanical and auto electrical, so i have gotten myself into some pretty nightmarish diagnostic probs. Now i really enjoy wiring. It is the part of the project that is seldom seen but can be the difference between trouble free enjoyable driving or sitting on the side of the road waiting for a costly tilt tray or a friend with a bit of spare time. Not to mention the frustration of headaches trying to delve into wiring harnesses. So i thought i might put up some helpful tips that i have learnt over the years. Ground points! I cant stress this enough. Clean ground is essential. Always remember the more gound points are better. Electricity is for the most part, fairly lazy and will always find the easiet path. So more grounds mean less issues. Connectors. We have the Internet now. So getting new connectors are easliy available and fairly inexpensive. Water proof plugs are very handy and now getting very small and easy to use. Education. Take the time to do a night class or similar. You'll be surprised at how much you can learn. Extra cable! If you it's the correct length, give yourself a a few more inches. Cable is cheap. Use new stuff. It doesn't have corrosion and will always solder nicely. Spend the time making the harness uniform and tidy. Plan ahead. Think about what circuits will be placed in which part of your project. I hate having to add wiring in to a new neat harness. Think about where heat and moving parts will be. If all else fails, jump on here and ask. Electricity is mostly invisible. There are many people on here with quite an expansive knowledge of antique wiring systems. I hope this go a little way to hepling everybody with their projects. Here are a few pics of a coupe i recently rewired for a friend. I found 5 circuits that were unfused and some wiring that was squashed between chassis and body! Dangerous stuff. Some before and after pics. Sent from my SM-G930F using The H.A.M.B. mobile app
Most people run from electrical work. It scares them because they don't take time to understand it. I worked with another mechanic at a dealership that would have an electrical problem and would jumper the fuse and say I just let the smoke out and I have found the problem. He burned up more stuff than I can remember before he got fired.
I was apprehensive about wiring my truck, I found good info on this site and American wire rep. I am taking my time for a clean install. Using and understanding relays took some time but I look at it as just a switch. Needed electric turn signal flasher for Led lights thought I wired them wrong when they didn’t work. Tie wraps were my friend to make clean look Good set of strippers and a good quality crimper helped Cheers
2x^ Support and secure your wires and harnesses. As a fire investigator I have seen MANY cars burn due to owner installed wiring that was haphazardly installed....the stories.....wow... Ground everything, run an extra black wire to all components. Make sure you color code your wiring, I mean don't change colors during a run......you will thank yourself if you have a problem. If you are cheap....get a fuse box from an older car and start from there. The kits make it easy with marked wires. Electricity is like water...it travels from one point to another and then back again (battery) Relays are a switch, they handle the high amperage that most manual switches cannot. (horn, blower motor, a/c compressor).
Great advice! although I kind of disagree with this: I prefer to use the body/frame to ground most components. Although this could take even more work than running a separate ground wire, if it's a typical rusty old car. I guess I just don't like redundant wires.
If you have access to a vehicle manual that has wiring diagram, use this and make a spreadsheet with lengths, colors, gauge of wire, etc. Then you can go back and recheck before actually making up the harness. As far as grounds, clean the metal, use star lock washers, then spray on something that keeps the oxidation down. Biggest ground issues are battery to block, block to chassis, chassis to body.
If I am doing a complete restoration. I will weld some 1/4" bolts along the top seam of the firewall. Great for hanging insulated cable clamps or a bracket later on down the road without drilling a hole in the firewall. Perfect place to put a ground wire as well. Since the stud is a permanent ground. I also paint the entire under dash white. Makes assembly a lot easier and working on it later when it's a lot brighter under there. Sent from my iPhone using The H.A.M.B. mobile app
This is not correct info , DC never changes direction . It's Direct Current ! AC is Alternating current , just wanted to clear this up for new guys learning . Sent from the frozen North
Good info here too: http://www.watsons-streetworks.com/tips Made me a big fan of relays " A current topic"
Ground...look at the trouble letters on here! Anything mysterious in old car electrical systems will turn out to be an inadequate ground. The future...when I wire up the main harnesses going up front or to the rear of car, I wrap in a 10 gauge unterminated piece of wire. That way if I decide to add in something like a backup wire or electric pump I have a neat source and not a lonely extra wire outside the harness. Pathological craziness...I like big wire. Early Fords, wire to 6V specs for 12 V use to make the electricity as comfy as possible, and I move up to 10 gauge for headlights and the central generator-ammeter-power wires. I HATE the look of the common red-yellow-blue terminals. It looks like "I wired my car right in the parking lot at K-Mart."
Nice work on the re-wiring. I cringe when I see some of the hack wiring on otherwise great looking old cars. I think he meant it travels in a loop, starting and ending at the battery. Kinda like the start/finish line on a circle track. Of course if you throw a charging system into the equation things get confusing.
Once it leaves the battery it doesn't go back , DC only takes what it needs and uses it. A alternator or generator is your supply source , the battery is storage . If you are pulling power from the battery the alt or gen tries to replace or overcome the draw. If you are pulling say 60amps and your gen or alt is 40 amps , you will in time drain your storage . On the other hand if you are pulling 60 amps and you have a 80 amps available , you will be able to maintain your storage as the extra amps will be put back into the battery . This all depends on engine RPM and quality of the system . But again D.C. Is not a loop on these old type charging systems . Sent from the frozen North
heh...I seem to recall having this discussion with someone else a while back, he seemed to think that it didn't matter what size ground wire you used, because DC only flowed through the positive wire, and didn't go back to the battery. Would you replace the negative battery cable on your car with a 14 gauge wire?
The ground size does matter , you can get away with running a smaller ground if the ground is closer than the power supply . But if the ground and positive are the same length they should be the same size . Sent from the frozen North
In my admittedly limited experience with building cars (if you consider 8 or 9 cars limited), 99.99999% of electrical problems seem to be associated with bad grounding.
Your post #15 suggests that you don't need a return path for the current. If you put an ammeter anywhere in the DC current LOOP of a circuit and it will read the same. Read your post again, and if you change your mind we'll go deeper into the subject.
Please explain your theory to me , as I have a very good understanding for line load and amp draw . So I understand that as you add connections and switches the amps and draws change . But let's say you have a 12 volt starter motor and it is grounded to the motor , the battery is grounded to motor . If you run this motor when and where does the power go back to the battery . Sent from the frozen North
It's not theory, and I'll use a part of your question as the answer. "you have a 12 volt starter motor and it is grounded to the motor , the battery is grounded to motor" The engine is just another conductor. I could also add the fact that electrons flow from "negative" to "positive" but that would just add confusion.
So are you telling me that the power goes through the starter and back to the battery ? Ok I see what you are saying , there is a current flow . But being direct current its flow path is unlike AC . Sent from the frozen North
Current flows in a loop. If it's DC, it always flows the same direction. If it's AC, it changes direction (and back) 60 times a second. But it still flows in a loop.
Yes agreed , I was getting caught up on the battery taking the power back through the negative cable or ground . I was getting brain cramped Sent from the frozen North
A case study in ground path energy: Some cars have a ground strap from engine to chassis or battery, others hope engine mount bolts and such will do the job for free. In the late 1970's GM made a lot of cars with no ground strap, and got back a lot of seemingly non-electrical problems for their design sloth. Throttle cables and trans kickdown cables were sticking or locking up entirely. It was discovered that the exceptionally poor groundpath had routed ground return through the cables, MELTING the plastic cable cowers or sometimes the cables themselves. Starter and running ground loads were going through cable that probably amounted to 16 gauge wire, and the amperage was sufficient to toast them.
Back in the early 70's I made my own wiring components,I used blank circuit board to make my fuse block and bought the glass fuse holders, connector strips,wire and connectors from radio shack. When wiring kits became readily available I tried several of them and although they all did the job some were better than others,cost was a factor in how complete the kit was. It is disappointing when you purchase what you are led to believe everything is included only to find you still have to buy additional components. About 11 years ago I tried the American Auto Wire kit and I was sold on it,everything is in this kit including more than enough wire that is printed with the gauge and component it attaches. This kit is so user friendly even the most inexperienced builder can wire a car like a pro. I have seen and corrected wiring messes very similar to what the OP posted,taking the time and planning where you run the wire is not rocket science,it doesn't have to be something you dread and have to hire out. HRP
The Jalopy Journal
