510 Chassis Wiring Size

[jeffball610]

Now that my project car is on the road, I need to start cleaning things up. One of the first steps is to clean up my rats nest of wires. Some of you may recall that I wanted (and basically did) a complete rewire of the system with a modern fuse/relay panel and other "upgrades" to the system. After doing so, I realized that I made a few mistakes and also had to add a few unplanned circuits to pass inspection for road worthiness.

 

Looking at the system, I would like to replace all (or most) of the wiring due to splices, unnecessary circuits on plugs, and some corrosion of the original copper wiring and brass terminals. I'm not entirely sure of the wire sizes and not sure how to measure what's there. I could do a Google search, but thought it might be beneficial for others to have some hard data to refer to if they plan to do something similar.

 

This gentleman has the appropriate connectors for those wanting to keep the original connectors. I'll probably keep most of mine since they are in good condition, but several others will be replaced with more modern weather resistant units.

 

I'm not sure where to look for wire sizes or specifications on the original system. I'm planning to use Tefzel Mil-spec wiring and Raychem coverings for both the chassis and the rework of my engine harness for longevity and a more professional direction my build is taking. If anyone has specs or suggestions, I'd love to hear them. If someone else has done this, it would be great to see some detailed information on what you used and how.

[datzenmike]

Well you can't go wrong with thicker than the original wiring.

[jeffball610]

Well you can't go wrong with thicker than the original wiring.

I agree, but keeping a thin harness saves precious space when you need to run 10+ wires somewhere. I'm sure I could try and do math to figure out the requirements for what is there, but I just thought someone had some of this info they'd like to share.

[MikeRL411]

Buried in the trunk of my RL411 is an early repair and reference manual.  It contains the wiring schematics of many early Datsun/Nissan vehicles and includes the wire sizes [in metric of course] on the schematics.  Most surprizeing was the fact that there are significant wiring differences between many "same year and model" sedan and station wagon wiring harnesses!  If originality is your thing, let me know and I will post the book name, publisher and ISBN reference number.  Barnes and Noble book stores can track down existing stocks of this manual if they exist [i  even got a copy of the "Book of Kells" bible thru them. Not an original of course, a photo reproduction page by page.  One of my ancestors was responsible for at least one of the 4 books].  It is a real hassle to copy individual schematics to the web.  Blown-up copies by snail mail seem to work best.

[datzenmike]

I agree, but keeping a thin harness saves precious space when you need to run 10+ wires somewhere. I'm sure I could try and do math to figure out the requirements for what is there, but I just thought someone had some of this info they'd like to share.

 

There's no shortage of space for wiring in a 510.  Harnesses do not have to be round, they can be flat for running along a floor to the rear tail lights..

[DanielC]

Wiring size is based on the current flowing through the wire.  A good place to start is house wiring circuit breaker sizes.  15 amps, 14 gauge wire.  20 amps, 12 gauge wire.  30 amps, 10 gauge wire.

But if you use thicker wire than that norm, lights will burn brighter, and motors will spin faster.  Using "too thick" of a wire (cable) in the starter circuit lets the starter spin faster.  This means the starter draws less current, and that leaves more voltage from the battery for the ignition circuit.  The engine starts sooner, and with less drain on the battery.  This means the alternator does not have to work as hard to recharge the battery.

[jeffball610]

Wiring size is based on the current flowing through the wire.  A good place to start is house wiring circuit breaker sizes.  15 amps, 14 gauge wire.  20 amps, 12 gauge wire.  30 amps, 10 gauge wire.

But if you use thicker wire than that norm, lights will burn brighter, and motors will spin faster.  Using "too thick" of a wire (cable) in the starter circuit lets the starter spin faster.  This means the starter draws less current, and that leaves more voltage from the battery for the ignition circuit.  The engine starts sooner, and with less drain on the battery.  This means the alternator does not have to work as hard to recharge the battery.

These sizes are not a good indicator for auto purposes. 14AWG is actually pretty big and can handle much more than 15amps. One of the many factors we have to consider is wiring distance. Cars are much smaller than houses. Wire type is also a factor in my opinion. I'm sourcing 19 strand 20AWG wire for most of my engine harness. This is about the same as factory (1990 Mitsubishi) but superior in every way.

 

Mike, if you have some wire sizes, it would be appreciated. I have factory service manuals for DSMs and they list all the wiring sizes in metric as well. .5mm is 20AWG and is the most common on the motor. The other 2 common sizes are .85 and 1.25. I don't know what wire gauge size that is yet, but it's used for power and ground wires throughout the engine and ECU.

 

My guess is that most of the Datsun stuff is 20AWG with high draw items like headlights, ignition coil, and blower motor being in the 14-16AWG range. Hopefully someone can correct me and get some real data here.

[thisismatt]

Cool thread.  A quick search brought up a few possibly helpful pages:

 

Wire size calculator: https://www.wirebarn.com/Wire-Calculator-_ep_41.html

 

Wire & wiring guide (with table of gauges/length/amperage): https://www.tessco.com/yts/industry/products/itm/automotive/get_wired.html

 

Another table: http://info.waytekwire.com/blog/automotive-wire-gauge-guide/

[shacks510]

I made a new headlight harness using 14 gauge wire with a separate fuse and relay for the low/high circuit, powered from the battery. Lights are bright but they're sealed beams, so the light pattern is pretty concentrated. I figured 14 gauge would be plenty for whatever upgrade down the road.

[jeffball610]

Cool thread.  A quick search brought up a few possibly helpful pages:

 

Wire size calculator: https://www.wirebarn.com/Wire-Calculator-_ep_41.html

 

Wire & wiring guide (with table of gauges/length/amperage): https://www.tessco.com/yts/industry/products/itm/automotive/get_wired.html

 

Another table: http://info.waytekwire.com/blog/automotive-wire-gauge-guide/

Good stuff. It takes a little math, but this is very helpful. I'm sure there are more guides out there. I was just curious about the stock system, but if someone is going to rebuild the whole thing, you might as well use new components and the knowledge we've gained since these cars were built.

 

I would suggest everyone take a look at your wires. I had to put a new connector on one last night and had some corrosion to the copper wire beyond the end where it's exposed to air. I'm sure all of the wiring has some extra resistance in it from years of use and corrosion.

[datzenmike]

Voltage, is what pushes current through a wire.

 

A 12 v headlamp rated at 55 watts will draw 4.58 amps but when charging, the voltage is 14 + volts and will push more current through it. This is true of the wiper, heater... anything.  A12 volt supply will suffer from resistance losses more so than a 120 volt household supply and why transmission lines are 550,000volt. If you have a 20 gauge wire replace it with anything larger. You can't go wrong with wiring capable of carrying higher currents. Car makers use the smallest gauge wire that they can get away with.