Technical Hot Rod Wiring: Tips, Tricks, Videos, & Pics

I googled "Wiring tips and tricks HAMB" and most of the threads were 10+ years old. Still good stuff but it might be a good time to share what we've done, see, or come across in new thread.

I'd like to make a harness that's clean, well run, good looking, easy to diagnose future issues and so on. Any help is appreciated - I'm looking forward to learn.

Thanks!

 

From @Paul

 

For what it's worth, maybe you'll get some ideas here... I used the 28 circuit Painless trunk mounted battery wiring kit..

https://49fordcoupe.smugmug.com/Wiring-the-Car

Link to their kits... every wire is printed every few inches..
https://www.painlessperformance.com/

 

I drew and shared the diagram in post 2 of a friend's car I was working on
then re-drew it (post 5) and posted it to my '23 build thread.
I had help from several members here drawing both of them and both worked flawlessly.

 

We make our own wiring harnesses at work for the mahogany boats we build. One of the most important things to do is great grounding . Another is solder the connection and shrink wrap it. One cool thing we do on our connections is when we shrink wrap it in black make a small label and then shrink wrap it in clear. This way the wire is labeled cleanly and close to the connection. We also make a chase for the wires and put a pulling string in it..

 

Thanks to all for the info. Saw some new things. Following along.

 

Pics please!!!

I love stuff like that. What are the labels made out of?

 

Excellent Information Thank You

 

Yes! An amp gauge and generator!

 

Battery in trunk threads that are worth reading:

https://www.jalopyjournal.com/forum/threads/battery-in-the-trunk.980110/

https://www.jalopyjournal.com/forum/threads/small-battery-reccomendations.1175066/

https://www.jalopyjournal.com/forum/threads/locate-battery-in-trunk-what-gauge.1191264/

https://www.jalopyjournal.com/forum/threads/trunk-mounted-batteries-what-size-cable-4-0.548891/

https://www.jalopyjournal.com/forum/threads/battery-in-the-trunk-please-school-me.508212/

https://www.jalopyjournal.com/forum/threads/trunk-mounted-battery.557326/page-2

https://www.jalopyjournal.com/forum/threads/changing-location-of-bat-to-trunk-ga-of-wire.1247332/


There are plenty more out there... still digging in.

 

This is what I use to make labels, they are adhesive backed but I always clear shrink them.

 

Tips.

good grounds. The current car I’ve created a bar under the dash with welded on studs for things to ground to and then that bar has a ground cable to the frame.

Be patient.

Mount the fuse box first and somewhere you can actually work on it

Add more patients

I also shrink wrap all connections. On top of making them more weather resistant I feel like it’s less likely to fall apart if your mechanical connection fails.

The last one I did I laid it all out in a big table and split it between dash, engine bay and the rest and losely bundled it.

last one I’ve got for the night is using asphault impregnated cotton looming to run bundles in. I also use it for headlight wires that run through exposed areas.

under the hood I put the entire bundle threw the looming, then at any points where a wire may need to branch off I poke a hole and exit the wire and then cover the exit in the looming with black heat shrink. At the end of the looming I also black heat shrink the end more or less shut/ tight to the wires. Does a great job keeping them safe, in place, “correct” looking and it doesn’t really draw attention. Occasionally I’ve used rubber coated adel clamps to help rout the bigger bundles.

something I haven’t done but like the idea of is using a weather pack type connector on the back of the dash so you can wire it on the bench and get it all tidy, then bolt the dash into the car and pop the connector together.

 

Get some of this stuff to start with.

 

Just starting to wire the truck. Last night I built this hinged flip down panel that bolts up under the dash. This way I can sit on the seat and wire up the terminal strips rather than laying on the floor (which is hard to do these days). Will help for any issues down the road as well. Label everything and have a good drawing.

 

Would 100% advise buying a box of assorted heat shrink sizes. I have two that have probably 15 different diameters in 3” lengths in both red and black. the size I use most of the time
I got a 12” spool of for a birthday and cut the bit off I need.

Just one thing you know you’ll always need more of that you won’t have to stop progress to go get more of.

 

Keep it simple while planning; you don't need a 23 circuit harness when an 8 circuit will do.

If you do your own harness, you can also step up your wire sizes; it always feels to me the commercial harnesses we have installed have under sized wires.

 

That's 90% of the reason I won't buy an aftermarket harness kit...

 

Good timing on this thread. I am mentally getting ready to wire my wife's Lark when it comes out of storage in a couple months, and eventually my '54 Commander.

In my notes I have a Cole Hersee 24213 continuous duty solenoid noted for use in a rear battery application. My idea was to run everything through one feeding the main fuse panel. You would have one signal wire running through the car to a few different kill switches that would shut off everything. Not really for security since it takes 2 minutes to figure out what is going on and jump the solenoid, but for safety and future serviceability. I like the idea of being able to shut off EVERYTHING with the flick of a switch from the interior, under the hood, or from the trunk.

On my offroad truck I use a Blue Sea Systems 4 way switch so I can shut everything off, power the vehicle and front winch with one setting, or the rear winch as it's own system, or both together. It is IP66 waterproof and can be switched under load. I think something like this would work great in a hot rod. I also like the thought of an external push pull on/off switch.

https://modernracing.net/products/mr-750a-switch Looks like a cool product that combines a few of the above ideas. Probably overkill and $$$ but in the big scheme of things might be worth it.

SXL wire is supposed to be the best for automotive applications. Not sure where I read that ow why but you saw it on the internet so it must be true.

Waytek and Sherco seem to be good electrical suppliers where you can get industrial quality stuff in bulk.

Eaton, GEP, and Littelfuse make a variety of sealed bulkhead connectors and power distribution modules. Particularly the Eaton ssVEC series look cool. IP66 rated, with separate connectors for different systems that you can change as needed. I just hate the thought of screwing up a wire and having to rework the whole harness. for her convertible and my hopefully someday Bonneville car, having sealed components would be nice. It would also open up the option of mounting the panel under the hood.

@Crazy Steve what do you use for planning out your harnesses? A spreadsheet with current load and voltage drop would get a person going, but for us that are just starting out, is there something more visual that we could use for planning? Pen and paper? Software of some sort?

 

@Paul, why does your diagram have a flat screen TV towards the front?

 

@Rynothealbino , this is the battery disconnect that I use. It is not weatherproof.
https://watsons-streetworks.com/product/toggle-battery-disconnect/

 

I don't like the idea of using one relay to control ALL power. You're putting all your eggs in one basket. You don't want a relay or switch failure to leave you stranded, or worse yet, cutting power at a catastrophic time. Basic lighting, horns, and ignition are all safety functions that if they fail at an inopportune time could escalate into a disaster. If your concern is small draws (clocks, radio memories, alarm systems for example) that can drain the battery over time during non-use, a better solution IMO is add a separate relay to cut power to those items for long-term storage. A small multi-pole ice-cube relay would work for this.

As to harness design, everyone is looking for a magic bullet. Well, there isn't one in spite of the aftermarket harness suppliers purporting to offer one. Their 'one size fits all' designs can be adequate for a 'basic' car, but start adding high-draw items like cooling fans, compressors for air bags, high power stereos, power windows, ect, etc can quickly outstrip the 'basic' design requiring additional relays/circuits to compensate. The aftermarket's supplying of relay 'kits' for various circuits is a tacit admission of this shortfall. So much for a unified fuse panel....

Remember, every aftermarket harness kit I've looked at supplies the fuse panels with two #10 wires from battery power. Properly de-rated down to 24 amps, that gives you 48 amps total. If you need a high circuit count panel such as the common 23 circuit ones I see, that gives you only about 2 amps per circuit.

I do my design the old-fashioned way; paper and pencil. I supply printable sheets here (Wiring 101 | Page 7 | The H.A.M.B. (jalopyjournal.com) to help. What would be nice would be a program where you enter the load, wire length, and desired voltage drop and it spits out the wire size. But keep in mind that voltage drops are additive: a 5% drop from A to B, and another 5% from B to C leaves you down 10% at C. Personally, I don't want to see any more than 5% anywhere and would prefer to see 3% or less. Voltage drop is the main enemy here. Heat is number two, keeping as much of the harness as possible out of high heat areas is a best practice. Heat reduces ampacity and increases drop. This can't be eliminated but can be reduced. I'll also note here that bundling ALL wires together reduces their ampacity and increases heat generated, multiple smaller bundles are preferred.

Two suggestions when in the design phase. One, when drawing up a wiring diagram as-built, DON'T try to put everything on one sheet. Instead, draw each circuit separately, identifying each wire as to color and size. This will make troubleshooting much easier. Two, so you know what goes where, by using a 'map' of the vehicle, represent each 'bundle' as a single line and note what each bundle contains including wire colors/sizes. As examples, head and park lights/horns, engine (ignition/gauges), under dash, and rear (lights, fuel gauge) could each be a bundle. I know one of the big attractions of the aftermarket harnesses is the marked wires, but careful selection of wire colors in the bundles can make each one unique, reducing the colors needed and eliminating the need for lettering them.

 

Put the power center where it is accessible in a break down. I put this one under the seat of my PU. I added a light to help see what fuse is blown (hopefully not the circuit the light is on) and I glued the fuse box diagram to the door, so I know what fuse does what.

Even room for spare fuses and a puller.

If have fun wiring, you will likely do a better job of it. Unless you are high. Then you may want to hire an electrician. And carry a fire extinguisher.

 

Hey @Bandit Billy that's slicker than snot on a doorknob!

 

We use the Dymo label maker on the boats and gives it a nice label under the clear shrink wrap.
When we wired machinery and larger circuits, we would use the Brady wire markers. You basically use numbers to identify wires instead of names.
Lots of great information on this thread.