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PostPosted: March 22, 2008, 10:55 pm 
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"Here's a few tips on modifying the Miata electrical harness.

Note: This was done on a 1994 Miata. There may be differences between the generations.

Note: Here's where I downloaded the wiring diagrams from. The Haynes manual WILL NOT cover everything. I very highly advise against modifying a harness using just the Haynes manual. They do not cover half of the important items, and often do not show multiple wires--there are a lot of splices inside the harness, and some connectors have more than one wire coming out of one particular point. However, I used the Haynes manual to back this one up-- you might want to go scan the Haynes diagrams and staple/paperclip them seperate from the Mitchell diagrams.

http://www.madracki.com/miata/wiring.html

------------------

Before attacking the harness, it might be good to skim through the diagrams to associate yourself with items you think you will want to remove.

Here are some of the items I chose to delete:

-popup headlight system
-all external lighting
-all internal lighting
-power windows
-power steering
-power mirrors
-power antenna
-rear defogger
-interior heating and cooling
-radio
-cruise contol
-airbag system

There are others, but those were the main items.

The orange and blue connectors are airbag sensors. They are a real pain, as they go throughout the entire car, and they take up about maybe 1/8 of your harness. They also have their own module, the "diagnostic module" or "supplemental restraint module" as it is called in the diagrams. This is something you will notice in several areas--Haynes, Michell, and regular guys like us all have three different terms for some things, and you may spend some time scratching your head thinking "WTF?". Anything related with airbags goes, but still check where the lines go before snipping.

I found it best to spread the harness in the general shape it would have been in the car, and hammer a few nails in strategic points to keep it from getting all tangled when you are trailing wires. Definately strip all tape and loom before trying to remove anything, because it is completely impossible to track otherwise--especially to consider there are quite a few splices, too. I brought mine inside to keep things slightly cleaner, and I placed a 4x8 sheet of plywood on two of the sawhorses I used to hold up my build table.

My donor car had just about every option except the kitchen sink, and ABS. ABS has it's own module as well, so if you have ABS, you will have 4 modules--the ECU, the ABS, Airbag System, and Cruise Control. That makes a LOT of wires. At one point I counted over 100 wires thick--thankfully I just had the three modules.

Mitchell shows a "Main Relay" in the diagrams. We scratched our heads for a while, and finally, after me reading the wire colors to my dad, we figured out that is what is labeled as the Fuel Injector Relay on the main fuse box lid.

If you intend on removing the AC/heating, make sure you don't just hack the wires--the engine coolant fan relay is in the bundle. I ended up pulling all the wires on the driver's side harness forward from the firewall except the ground, the radiator fan, the MAF sensor, and the diagnostic port (not to be confused with the diagnostic module). When I finished the harness, I pulled the diagnostics port and the ground behind the firewall, so there are only two sets of wires on the drivers side.

The TNS relay, mentioned in Mitchell, is the running lights relay. I deleted it, as I will have headlights on/off and turn signals, no running-lights-only setting. This is not to be mistaken with the DRL setup (Canadian).

There are a few diagrams in the Mitchell package that mention DRL wiring. Just because we're not in Canada doesn't mean we don't have the wiring--I deleted a few junctions that simply looped. Also, some of the automatic transmission wiring found it's way into my harness as well, usually going to a connector, and then not coming out of the other end, always causing a flurry of double-checking and freaking out until I'd find what it was.

Which brings to mind: How do you intend on wiring your headlights? If you are not using the stock column assembly, i.e. the stalks for lights and wipers, you will probably be better off stripping the entire headlight/external light assembly out of the harness and make an external headlight harness. That is what I am doing. It'd be too much of a hassle trying to wire up switches and selectors for that, as well as the fact that you are no longer using factory lights--you will have different wiring, most likely. If you are using a pressure-switch brake light, then you will probably want to remove the entire rear light assembly. That's the entire bundle of wires that goes down the passenger door sill on back. It connects to the main harness, and then to the battery harness, but other than that, it is on it's own. I did not have to do any stripping or cutting there.

Floor mounted pedals not only delete the use of a brake light switch, but also the clutch switch that came with the Miata, so I deleted all the stuff that came from that, and the two large wires that go to the switch are power wires, and I simply spliced the one to another, as that was just a dead-switch, making the car only able to start with the pedal down. So I'll be able to start the car with the clutch up, but what moron is going to start in gear?

That covers everything I could think of while going through the diagrams again.

When splicing, unless you already have a crimping tool, they cost a bit. Usually 50-100 and up. You want the ratchet type--the cheap kind really suck, and you're not going to want to do 200+ crimps with them. Butt splice connectors tend to be pricey, depending on the type. I live about 15 minutes from a Fastenal, so I have quick access to them, although I heard Home Depot has them as well. However, the guy there stated over the phone that they are for larger bands, i.e. 6-12 gauge, rather than 10-12, 14-16, etc. You'll usually need about 100 of the red ones (22-18g, about 10 bucks), 5-10 of the blue ones, (16-24g) and 5-10 of the yellow ones. (12-10g) I chose the nylon coated type, there are vinyl, which tend to be cheaper, but are harder to crimp, the heat-shrink coated, which cost about 10 bucks for 25, and the heatshrink-and-self-solder type, which are REALLY expensive, and definately not necessary.

If anyone needs those parts, I can get them and ship them, as well as I'm willing to lend out my crimping tool if the person in question will pay for the shipping, and return it in a decent amount of time. I figure, it'd be easier to pay 10 bucks than 100 bucks--and I always ship fast.

If there's any questions about the Miata harness, I'd be happy to help if I can. Also, if anyone is relatively local and wants a hand with it (it really works better with two, one to read off wire colors and the other to match them with the diagram), I'm willing to help. "


Attachments:
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File comment: I put a few nails in strategic points, to keep the wiring from getting tangled.
0212082136.jpg
0212082136.jpg [ 62.55 KiB | Viewed 24904 times ]
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PostPosted: March 22, 2008, 11:00 pm 
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Joined: August 10, 2007, 12:05 am
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Location: Champion, Ohio
More pictures


Attachments:
File comment: What a mess.
0321082033.jpg
0321082033.jpg [ 52.82 KiB | Viewed 24902 times ]
File comment: The harness spread out in the family room, ready to be brought outside to measure for shortening.
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File comment: This is scrap wire, after having deleted some of the stuff I am not going to use.
0306080144.jpg
0306080144.jpg [ 72.28 KiB | Viewed 24902 times ]


Last edited by SteyrTMP on March 23, 2008, 11:03 pm, edited 1 time in total.
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PostPosted: March 22, 2008, 11:04 pm 
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Location: Champion, Ohio
And more.


Attachments:
File comment: If you look closely, you can see the four loops I taped to be shortened.
0321082224.jpg
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File comment: Tools of the trade.
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File comment: The final box of scrap wire. Heavy!
0322081418.jpg
0322081418.jpg [ 62.17 KiB | Viewed 24889 times ]
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PostPosted: March 22, 2008, 11:08 pm 
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Location: Champion, Ohio
More. I used just shy of 100 butt splices. That means stripping wire 200 times, and crimping 200 times... my poor fingers. Actually, it was not that bad, but my knees were killing me from kneeling on the floor for hours on end. It would have been nice to have had a large table to have done this on.


Attachments:
File comment: My largest splice/shortening... the ECU.
0322081410a.jpg
0322081410a.jpg [ 51.86 KiB | Viewed 24881 times ]
File comment: After shortening.
0322081410.jpg
0322081410.jpg [ 64.7 KiB | Viewed 24881 times ]
File comment: The final layout, as it will be in the car. The rear battery/transmission line is not in the picture, but that does not need to be edited.
0322081451.jpg
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PostPosted: March 22, 2008, 11:15 pm 
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Location: Champion, Ohio
Last bunch.

Next on the list is to install fuel lines, clean intake manifold, reinstall throttle body and throttle linkage, purchase CAI filter, and fab up the tubing for the CAI.

I have a MAF sensor on the way, it looks like I am going to have to replace the O2 sensor, as it is seized up in the section of tubing it was located in, and I have to extend the EGR tube to the exhaust header and install a bung for it.

I then have to re-route the heating piping, temporarily mount the radiator (no nose cone yet, so not sure of radiator location and angle yet), and hook up all electrical.

I have a Honda S2000 starter button on the way, and I am going to buy a two-position on/off key and switch from Digi-Key, along with circuit breakers and toggle switches.

I need to decide where I am going to mount the tach and speedo, as well as the rest of the dash, and I need to cut out knee-holes in the scuttle.

It's getting there, slowly, but surely!


Attachments:
File comment: Sitting with wires in general places.
0322082149.jpg
0322082149.jpg [ 63.79 KiB | Viewed 24870 times ]
File comment: I retained one of the factory rubber grommets for the main engine harness assembly--the driver's side only has two things going through the firewall--the radiator fan and the "intake fan"
0322082149a.jpg
0322082149a.jpg [ 68.88 KiB | Viewed 24874 times ]
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PostPosted: March 22, 2008, 11:47 pm 
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Looks like a lot of work. Hacking the Miata wiring harness is one of my next projects. Where did you get your wiring diagrams?

Oh and what are all of those blue and orange connectors that are everywhere? :P

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PostPosted: March 23, 2008, 12:33 am 
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I forgot to mention a general note:

When splicing, unless you already have a crimping tool, they cost a bit. Usually 50-100 and up. You want the ratchet type--the cheap kind really suck, and you're not going to want to do 200+ crimps with them. Butt splice connectors tend to be pricey, depending on the type. I live about 15 minutes from a Fastenal, so I have quick access to them, although I heard Home Depot has them as well. However, the guy there stated over the phone that they are for larger bands, i.e. 6-12 gauge, rather than 10-12, 14-16, etc. You'll usually need about 100 of the red ones (about 10 bucks), 5-10 of the blue ones, and 5-10 of the yellow ones. I chose the nylon coated type, there are vinyl, which tend to be cheaper, but are harder to crimp, the heat-shrink coated, which cost about 10 bucks for 25, and the heatshrink-and-self-solder type, which are REALLY expensive, and definately not necessary.

If anyone needs those parts, I can get them and ship them, as well as I'm willing to lend out my crimping tool if the person in question will pay for the shipping, and return it in a decent amount of time. I figure, it'd be easier to pay 10 bucks than 100 bucks--and I always ship fast :)


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PostPosted: March 23, 2008, 12:26 pm 
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chetcpo wrote:
Looks like a lot of work. Hacking the Miata wiring harness is one of my next projects. Where did you get your wiring diagrams?



I can supply any wiring diagram you need for autos from 80-03 and will have 80-07 soon. Just let me know how you want to receive them (posted individual on my site or one large zip file) and I will send them.

I guess I should post somewhere offering them. What do you suppose is the best section?

Gene

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PostPosted: March 23, 2008, 2:42 pm 
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Thanks Nate, that's an excellent write up. I was hoping not to have to hack through the entire harness if I didn't have to. I just want to trim some of the useless circuits. I don't mind a few pounds of extra wire bundled up as long as it's out of sight. :P
And Gene, if you don't mind it, a post in the "Interior" forum would be great.

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PostPosted: March 23, 2008, 4:17 pm 
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Chet, my only concern would be that you bind it tightly, then... there's a LOT of extra wiring lying around, and it would really suck for it to fall out while driving. I'm trying to think who bundled theirs up and it came out...


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PostPosted: March 24, 2008, 11:15 am 
I would highly recommend that anyone who's using a Miata donor buy a factory manual. You can get them for $101 from Trussville Mazda. They use consistent language throughout, they have far fewer errors than Haynes and they include a factory wiring diagram. Definitely worthwhile. I've never been a big fan of the free online diagrams.

Chet, have you tried turning on your lights yet? The TNS relay is not a running light relay, it's your taillight relay. Also, one of the clutch switches is not to prevent you from starting the car in gear, but to tell the ECU the car is at idle. This can cause some idle oddness when you have the car in gear and the clutch depressed. If the behavior changes when you put the car in neutral, that's why.

Good quality ratcheting crimping tool for $27.97: Del City. Get yourself one of the cool spring loaded wire strippers while you're at it - you can also find those at Home Depot for less IIRC.

Del City also sells quality crimp connectors, I prefer their heatshrink type without solder. Remember that the heat shrinking doesn't just provide weather protection, it also provides mechanical support to the wire.

I don't like the use the word "hack". It doesn't carry good connotations :) Remember that a screwup on your wiring harness can lead to a Locost bonfire.


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PostPosted: March 24, 2008, 11:30 am 
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Hrmm. The Mitchell diagrams are usually a rather expensive (I believe around 1000 a year for a shop) diagram provider for all sorts of cars. It's pretty thorough. 33 pages for the wiring diagrams.

The wires I spliced from the clutch pedal were the two heavy wires--and one went directly to the start key switch. The others were deleted, as there is no way of mounting switches to a floor mounted clutch. What did you end up doing for your wiring in that regard?

Wish I'd seen those prices earlier... it costed me around 50-60 bucks after shipping, and I did all the wire stripping by hand with a cheap wire stripper.

I considered the heatshrink connectors, but they were considerably more expensive, and as everything is under both a thick layer of tape and wire loom, with an extra layer of tape on top of that, and it is all under the scuttle, I'm not too concerned about weather protection. Anything that would have needed to have been spliced in the engine bay would have gotten weatherproofing. ::edit:: I forgot to mention--the factory crimps (Yeah, there are a few) were all using the cheaper vinyl crimps, non-heatshrinking. I used the nylon crimps. :)


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PostPosted: March 24, 2008, 12:14 pm 
Expensive doesn't mean good :) If you want bulk, the factory manual is 103 11x17 pages. But more importantly, I find it's a better diagram. After all, it was written by the guys who built the car for the guys who were going to service the car at their own facilities.

In my car, I don't have a clutch idle wire either. Of course, I don't have a stock engine computer. It's not liable to be a major problem, just be aware that you might get different idle behavior depending on if you're in gear or not.

I keep a big stash of those heatshrink connectors in my garage, they're amazingly handy to have around.


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PostPosted: March 24, 2008, 12:40 pm 
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I am going to probably end up going MegaSquirt once everything is up and running, so that should be able to take care of any idle issues. However, I don't plan on running on idle very often... :) My Mini never idles :D


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PostPosted: March 24, 2008, 4:34 pm 
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Keith Tanner wrote:
I would highly recommend that anyone who's using a Miata donor buy a factory manual. You can get them for $101 from Trussville Mazda. They use consistent language throughout, they have far fewer errors than Haynes and they include a factory wiring diagram. Definitely worthwhile. I've never been a big fan of the free online diagrams...


The FSM has a harness diagram in it that's good, but the factory electrical supplement is even better.


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