I debated putting this in the performance section with the wiring needed for some engine swaps, but with the age and condition of some of these cars there's going to be some maintenance needed on factory wiring I think. If a moderator thinks the performance section would be a better fit, please move it there.
The following are just my opinions and how I generally wire things. I've done a bit of research and had some trial and error in doing wiring, especially when starting with a universal harness and adapting it to an engine and chassis such as what I'm doing with my Kswap. These are the things that work well for me, if someone has a better/different way post it up as this is a board for discussion.
Planning
This is the first and hardest step in wiring IMO. It's pretty easy if you're just repairing factory wiring, as I just follow what the factory did unless there's a need to re-route the wires. If starting from scratch, I try to lay out the wires first and that will let me figure out the best spot for any splices if needed. I can then start splicing and looming the wires then finally crimping on terminals and connectors. The main considerations are also making sure you use the right size gauge for the current, staggering the splices so the wiring doesn't have a large lump in one spot, and making sure it's protected if not covered by a factory panel or anything, such as being in the engine bay or the frunk. I also try to make my wiring not as noticeable for a clean install as well.
Wire
For new wire I use TXL wire for about everything. It's rated to a higher temp than PVC coated wire and is more flexible. There's also GXL and SXL, with the differences being insulation thickness. For that it goes GXL>SXL>TXL from thickest to thinnest. There's other options as well but the main things are looking to make sure it meets SAE specs, is stranded, and is the proper size for the load it'll carry.
Connecting wires
Simply put, soldering is for circuit boards, not joining wires. A crimped connection will be stronger than a soldered connection and will not crack and fatigue from vibrations. OEM manufacturers do not recommend soldering and you won't see it on track cars either. With crimping though, I don't use the red/blue/yellow generic connectors from the parts house. I use non-insulated barrel connectors with adhesive lined heat shrink. The barrel connectors are very versatile as you can get reducing connectors if you need to splice multiple wires into one such as a shared ground or shared power. You can also use shorter standard barrel connectors to do the same thing, using one size larger to make a 2 into 1 connection. I prefer these anymore as it makes for a shorter, easier splice and only one crimp overall.
Protecting wires and crimps
For covering the non insulated butt connectors as I mentioned earlier, I use adhesive lined heat shrink. As it shrinks, the adhesive melts and makes a water tight seal, further protecting the joint. When re-looming wire, I don't like using the split sleeve corrugated sleeving as it cracks over time. Many OEMs use this, but if you've handled an engine wiring harness in the spyder, you know how fragile it becomes with age and heat. I like using expandable sleeving, it looks better, is more flexible, and a little more durable than the corrugated split stuff. Sometimes when I can't access the end of wires, I'll use the split sleeve that looks similar to the expandable sleeving, using a wrap of electrical tape on each end of the sleeve and sometimes one or two spaced out depending on length.
Connectors
This is where it gets fun. You can sometimes get the OEM connectors and pins from the dealership for a reasonable cost. Other times you can use a 3rd party source for connectors that will work with OEM connectors. Ballenger Motorsports is a good resource and there are others as well. If joining wire harnesses, there's a couple of options, with the ones I like being the deutsch and metri pack connectors. They're affordable, easy to use and seal up from the elements. One thing to note about connectors is making sure they are either push to seat or pull to seat. A push to seat connector, you will crimp the terminal on the wire then push it in from the back side. A pull to seat, you will thread the wire through the connector, crimp the terminal on, then pull the wire back through, seating the terminal in the connector. Some metri pack connectors are pull to seat and many common pressure sensor connectors are pull to seat as well.
There's probably things I'm forgetting, overlooked etc. but will add some more info I'm sure.
Topic starter
Posted : September 28, 2019 11:24 am
2
I moved this to the DIY how to section. Great write up. I especially like the part about crimps over solder.
Posted : September 28, 2019 11:45 am
1
Want Pics!
Get your Short Antennas, Decals, and all sorts of goodies at:
https://takubanmotorsports.com
Posted : September 28, 2019 12:12 pm
...and want sources, links!
I make Amateur Armrests - see the Commercial Forum. I also have SMT repair seals available.
Posted : September 28, 2019 8:39 pm
1
@dev, thanks, I wasn't sure of the best place to put this.
@lordtakuban, I don't have many pics of my wiring, but I'll upload some today and try to take a few this week while I'm working on my car.
@cyclehead, For sources and links, I order a lot from McMaster-Carr their 3:1 moisture seal heat shrink is actually RayChem brand and very good. For wiring, I use Wire Barn. For connectors, I usually use Ballenger Motorsports, Mouser, or Digikey. I use the butt connectors from Ballenger as well. The parallel connectors are what I generally use for splicing multiple wires into one. I also use McMaster for most of my expandable sleeving as well. Sometimes even amazon and Ebay have good deals on wiring supplies, just check the specs for everything before ordering.
Here's the guide I use for splicing as well.
Topic starter
Posted : September 29, 2019 10:56 am
2
Good info...
When sizing wires for wiring up devices, the fuse or breaker is sized to protect the wiring, not the device being powered.
Fuse: You need to know/determine the normal operating current of the device under load (being connected) and then multiply this value by a safety factor of 1.25 -> 1.56 to ensure the fuse doesn't blow during normal operation, then select a standard value fuse or breaker that is slightly greater than this value.
Wire/Cable: Once the fuse has been selected, the AWG wire is sized based on an ampacity that is greater than fuse selected and the wire must have insulation properties that can handle the extremes in operating temperature and environment for the Fuse selected. Normally the wire ampacity must be de-rated based on the extreme operating temperature that the wire might be exposed to. A good rule of thumb is to select a wire ampacity that is at least 2-3 times as great as the selected fuse.
When crimping wires, use a high quality mil-spec crimper and you will never have an issue with connector failure when used correctly.
If you choose to use a cheap crimper, chances are you will never be happy even when using and adhesive heat shrink covering the crimp.
Just a few more things to think about when wiring.
Mono Craft GT-300 with a few upgrades...
Posted : September 29, 2019 1:54 pm
2
Thanks for adding some great info @neomr2!
Something I forgot to mention about planning and keeping everything organized, a label maker that can print on heat shrink is a great investment. I've got a Dymo Rhino 4200 that works great for wiring and many other projects, car related or not. Here is my IAT sensor wiring. I used compatible heat shrink but didn't heat it when I slipped the wires through. They still stay in the heat shrink very well.
In the next pic you can see where I've started looming some of the wires. There's also a ground splice for the coil packs in the left of the pic. Out of the picture to the left is another piece of heat shrink slid over the loom so that after the coil pack wiring is tidied up, I can slip it over where the wiring splits which will keep the loom from fraying and make everything look clean.
Topic starter
Posted : October 1, 2019 6:58 pm
2
I mentioned pull through connectors in a previous post and was dealing with a couple last night wiring in oil and fuel pressure sensors so I figured I would take a few pics. These connectors, you'll slip the wire seal on first as usual, but then slip the wire through the plug before crimping on the terminal. This is where the planning part is a little more crucial. Instead of being able to just unpin and repin into the right location if you mess up, you have to slide the right wire through the right hole before you really start. Here's the wire seals on and wires slipped through their correct holes.
Another thing I never went over with on some tools. There's different crimpers for different connections. I use standard crimpers for barrel connections and the simple stuff. I use specialty crimpers similar to these for crimping most pins for connectors. Here's a pic of the type of crimp it creates.
That pic is of the signal wire for the oil pressure sensor, if it was a push through, I would have crimped the wire seal in the end instead of just the unstripped wire.
Topic starter
Posted : October 6, 2019 2:07 pm
1
"They" say "You can tell how often a car has been repaired by a DIYer, by the number of zip ties you can see in the engine compartment."
While I have never found this comment funny --- there are just so many places where a well placed zip tie trumps just about any other fastener --- I have to admit that zip ties installed on cars routinely cause me to shed blood. The problem is: when you cut the "Tail" of the zip tie off with dykes, most wire cutters, and/or scissors it leaves a rectangular piece of protruding plastic with two very sharp edges. It is those sharp edges that love to gouge you when you are thrashing about in the engine compartment.
Here is the solution: use toe nail clippers (the cheap folding ones work just fine) to cut the "Tail" of the zip tie off. The toe nail clippers cut the tie much closer to the lock so that there is almost none of the plastic "Tail" protruding and they leave a round end on the tie's "Tail" so there is nothing to rip your skin.
Try it and prove it to your self. After you do so, if you are like me, you will add a toe nail clipper to your auto wiring Kit.
Paul
This post was modified 5 years ago by Not 2 Old For 2 Seater
Posted : October 9, 2019 9:23 am
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Nothing at all wrong with zip ties. Easy to install, easy to remove by using a sharp scissors and for the engine compartment they can handle the heat. I have used them on the rear bumper due to the fact that the fasters holes have rounded out.
Posted : October 9, 2019 9:53 am
I bet dollars to doughnuts that far fewer zip ties fall out than those brittle plastic garbage-y pop-in thingies. And for easily half the price.
🐸, 2003, Electric Green Mica
Posted : October 9, 2019 12:43 pm
I bet dollars to doughnuts that far fewer zip ties fall out than those brittle plastic garbage-y pop-in thingies. And for easily half the price.
Absolutely. Manufactures go for neatness because zip ties are an eyesore. There are other methods that look like crap and to be laughed at like using Gorilla tape to hold down my light weight battery in the frunk temporarily until I could build a proper mount but it worked so well that I forgot about. I eventually undid everything and moved the battery to the back but this time did it right with a mount. Either way works but one ends up clearly embarrassing.
Posted : October 9, 2019 1:39 pm