Hey guys,
What's a good way to go about this? In my mind, I imagined bundles of wires that had to go from point A, where they did something (sensor, light, etc) to point B where they got controlled (switch, ecu, etc), with maybe a little bit of daisy-chaining and some extra wires for grounds. Clearly, I underestimated this job. I had hoped to separate out cords of wires that went to a similar place, perhaps with a similar purpose, that I could lengthen/shorten/eliminate.
I've armed myself with Craig's ID thread, the FSM, an assortment of tools, and a trash can. But I'm having a heck of a time untangling this mess.
Do I just cut some wires, untangle, lay everything out, and solder back together? Mark the connecter a wire goes to, cut close to the connector, untangle, lay everything out, then get some pins and re-pin it one at a time?
There was a good long post about dieting not too long ago.
Do an advanced search for it. Just what u need to know.
I would not cut any wire w/o labeling ea end.- like a,b ,c etc
I found 2 that referenced Bob's thread (likely the holy grail). Guess I just wanted a little push that I am, in fact, CUTTING most of the wires to get everything untangled.
I built my roadster using a 1996 mustang gt donor. Dieting the wiring harness was one of the most tedious, and anxiety inducing, parts of the build. Of course I labeled every plug, but have to admit "we" actually mislabeled one very important pair. Because of one stupid mistake, I spent hours hunting down the error. Lesson learned? Be very careful when you label your wires and plugs, and don't make stupid careless mistakes.
I would also recommend that you write the labels yourself. Don't yell out to an assistant/kid/spouse "write label 'AA'". Write it yourself. The more people involved, the more likely something will go wrong. And if anything does go wrong, you're too blame, not someone you love.
Second stupid mistake: I threw away what turned out to be a very important sub-harness, thinking I didn't need it. Lesson learned? Don't throw anything away until your car is complete and working properly. Fortunately, Ron Francis Wiring makes a replacement harness for the section I threw away. It cost me $90, but saved the day.
Although it is not recommended, I dieted a lot of wires before my first start up. Things like the heater fan, stereo, window motors and wipers were easy to keep track of and remove. But all other wires and plugs (other than those referred to as stupid mistakes) were kept intact until the car was running, and all electrical hardware working properly.
I was lucky enough to find and buy an original copy of the 1996 Mustang Electrical and Vacuum Troubleshooting Manual, which has well over 100 pages of easier-to-read wiring diagrams for just the 1996 mustang. I think it is published by Ford. I never could have completed the wiring, or the car, without it. It was especially helpful when wiring up the gauges in the dash. I used gauges made by a company in Florida called Dolphin Gauges; I think their gauges look great, and are very reasonably priced. Here's a link to the set that I used - https://www.dolphingauges.com/produc...ogrammable-set - But I still needed the ford manual to get it wired up right. The manual is also necessary when check for continuity and grounds.
Pay attention, work slowly, write clearly, and throw nothing away, and you should be fine.
Joel
There is a series of posts in my build thread you might find helpful.
Thanks. I'll check it out. It's hard for me to keep track of which genius did what, and which guy wrote particularly helpful posts in what forum. So many people here who are really good at something, and I just can't keep everyone straight!
Originally Posted by Joel Hauser
...Pay attention, work slowly, write clearly, and throw nothing away, and you should be fine...
Sage. I remember when I worked at a machine shop, part time (I had two other jobs at the time, so....) Boss's wife ran the office, came out and took some pictures of an engine I tore down because the rods were fubar'd. I asked what she wanted me to do with them, and she said "Chuck em." Bossman showed up after lunch...NONE too happy. Cussed up a storm, and I almost didn't go back. Either way, learned THAT one. I do have the FSM, and I started my engine about a month ago. Only got codes I was expecting (TVG etc).
I would suggest a wiring diagram that matches your harness. Make sure they match. With mustang diagrams, i have two different ones for the same year and they are not the same, and one shows the changes for CA cars.
Spend some time with the diagram and the harness untill it starts to make sense. Then you will be able to see what and how things can be cut out from the diagram.
I also copied the diagram so i could write on it and mark what has been cut or changed. I would not want to diet with out one.
A wiring diagram is an absolute must and I was actually pretty impressed with the Subaru diagrams. The method I used was to label every plug. Then I removed plugs I knew I didn't need and took the wires back as far as I could. If I wasn't sure about something I left it. Once I had everything removed I put the harness in the car and shortend a lot of the wires. It was easy enough to do that in car even though there are a lot of wires to shorten. In the end I was pretty happy with the results. It took a couple of months for me to get through it. I would probably try to take a few more wires out if I were to do it again, but he car started on the first try and has been running well since. I hadn't ever done anything with wiring harness prior to this. Just take your time!
I agree with everything guys have posted about this above.
I dieted my 818 harnesses because I was one of the first builders with frame #25 and there were no alternatives at the time. For the Mk3 I built previously I had a vendor, I-Squared, diet my engine harnesses and build a body wiring system. This time, I had to learn how to read the wiring diagram and I had the long thread by Mechie3 showing the terminals. It took over 2 months and I had to walk away many times in frustration. The engine started the first time and, after finding & fixing a DBW mistake, it’s still running well at 4,500 miles. Now, you’ve got lots more help from the smarter guys on this forum, like Bob_n_Cincy, K3LAG and others. I learned a lot by dieting my wiring, especially patience, perseverance and also patience.
Untangle your harnesses carefully without cutting anything. You’ll have to carefully cut and unwrap the OE sheathing, of course.
Label each terminal with a tag that won’t fall off. I used paper tags with wire ties. Make sure each is correct by the color, size and shape and also by the wires shown in Mechie3’s pictures and the wiring diagram. Double check.
Cut out the wires that you know aren’t needed, like air bags and security system.
I laid the harnesses over the chassis to know what to lengthen or shorten but now you have better ways shown by the wiring gurus on this forum. Unless you have lots of soldering experience, I learned it's best to crimp.
Don’t trash anything until it’s done and running. Have fun. And patience.
Oh, my one mistake was not knowing about a dotted line in the wiring diagram. The DBW throttle has 5 wires that I cut and lengthened. One wire has a woven sheath that is grounded but I didn’t know that, which caused the engine to run rough. Eventually I learned that it is marked with a dotted line in the wiring diagram and replaced it with sheathed wire. Other wires have dotted lines around them, so watch carefully.
Did I mention Patience?
818S/C : Chassis #25 with 06 WRX 2.5 turbo, ABS, cruise, PS, A/C, Apple CarPlay, rear camera, power windows & locks, leather & other complexities. Sold 10/19 with 5,800 miles.
Mk3 Roadster #6228 4.6L, T45, IRS, PS, PB, ABS, Cruise, Koni's, 17" Halibrands, red w/ silver - 9K miles then sold @ Barrett-Jackson Jan 2011 (got back cash spent).
I will post all 10 pages of my schematics. Is there a way to post PDF diagrams?
Bob
If Microsoft onedrive works, here is to my schematics. My donor was an 04 forester XT 2.5L DBW w/AVCS which has a lot in common with a 04 STI. Some minor differences with a wrx.
I agree with everything guys have posted about this above.
Untangle your harnesses carefully without cutting anything. You’ll have to carefully cut and unwrap the OE sheathing, of course...
Cut out the wires that you know aren’t needed, like air bags and security system...
I laid the harnesses over the chassis to know what to lengthen or shorten but now you have better ways shown by the wiring gurus on this forum. Unless you have lots of soldering experience, I learned it's best to crimp...
I agree, great advice here...that's why I took a moment. I did manage to unwrap the harness without cutting anything, but untangling it is another story. Ain't gonna happen. That thing is a mess. I did ditch the airbag system (still have the wires, though!). I do have my fob, and I was expecting the security system to work, so I've kept it so far. Does it need to go?
I also saw Touchstone (and I believe somewhere in Bob's giant compendium) of measured rope to lay out the harness path. Seems like it should work for me, but only one way to find out.
As for soldering, I'm competent and I've put more than a couple stereo systems in cars I've owned, but it's hard to beat crimps for speed, if nothing else. I saw a strong argument for crimps being adequate on conduction of most electrical signals and superior in terms of flexing (the solder joint is very stiff and fails after being bend a few times) but I don't expect these joints to flex much....so I'm undecided on that count. Speed, though, that's important, too.
Originally Posted by Bob_n_Cincy
I will post all 10 pages of my schematics. Is there a way to post PDF diagrams?
Bob
Bob, thanks a ton. Your link did work, and I'm looking through them. My build is for the street, so there are going to be differences, for sure, but I like the way you laid everything out. Very clean. Feels like I'm scrolling back and forth a lot with the FSM trying to see where a wire starts and ends.
Originally Posted by STiPWRD
I followed Larry's thread:
1. Label all connectors
2. Unwrap all sheathing
3. Cut away unneeded connectors and wiring
4. Put dieted harness in car and shorten extend as needed.
This all took me about 80 hours.
Thanks STiPWRD, I'll be sure to check that one out, too, before the weekend. I did label all my connectors, but it was before I really comprehended what I was getting into, so I labeled them in a way that would be easy to plug everything back together. If I had it to do again, I'd probably spend the extra time labeling them by the codes in the book. I might still try to do that, but I scribbled on the flat parts with sharpie already. Maybe if I wrap them in masking tape, then I can scribble on that. Big takeaway for me is that getting started was the hard part.
Bob, thanks a ton. Your link did work, and I'm looking through them. My build is for the street, so there are going to be differences, for sure, but I like the way you laid everything out. Very clean. Feels like I'm scrolling back and forth a lot with the FSM trying to see where a wire starts and ends..
My build was also for street. I wanted my car to be minimalistic. No radio, no Hvac, and minimal creature comforts. If you notice in my drawing I eliminated the interior fuse box. everything in orange is internal the MB fuse box. I made my own circuit for the wipers and lights. Everything from page 4 on is simplified OEM.
Bob
Thanks STiPWRD, I'll be sure to check that one out, too, before the weekend. I did label all my connectors, but it was before I really comprehended what I was getting into, so I labeled them in a way that would be easy to plug everything back together. If I had it to do again, I'd probably spend the extra time labeling them by the codes in the book. I might still try to do that, but I scribbled on the flat parts with sharpie already. Maybe if I wrap them in masking tape, then I can scribble on that. Big takeaway for me is that getting started was the hard part.
I agree, getting started is the toughest part and it does take some time to label everything. But once things are labeled it makes life soooo much easier and things tend to speed up from there. I just used blue painters tape & sharpie to label the connectors, worked well for me. It also helps to have a list of everything you want to remove once you begin dieting. I ended up soldering everything because I feel crimps will make the harness way too bulky - there are too many mods to the harness to use them IMO. I know some swear by crimps but I prefer solder.
I agree, getting started is the toughest part and it does take some time to label everything. But once things are labeled it makes life soooo much easier and things tend to speed up from there. I just used blue painters tape & sharpie to label the connectors, worked well for me. It also helps to have a list of everything you want to remove once you begin dieting. I ended up soldering everything because I feel crimps will make the harness way too bulky - there are too many mods to the harness to use them IMO. I know some swear by crimps but I prefer solder.
I thought I saw some super tiny crimps somewhere, non insulated. I'm going to be a good boy with the heat shrink, too. If those crimps aren't as small as I think they are, or if I just can't find them, I'll be back on the solder wagon, too.
Turbo
This is a picture of the harness for my second car.
For crimping I use NON-insulated barrel connector with Adhesive lined heat shrink. Ideal Crimp tool#429 second.jpgtool.jpg
Last edited by Bob_n_Cincy; 09-12-2018 at 12:44 AM.
It's slow going, but pretty smooth. Hit a bump or two labeling some of the connectors, but I think I got it all straightened out with the correct labels. Right now I'm taking everything apart, then I'll separate out the things I want to keep. I'm pretty sure I end up with a lot more labeling than perhaps I'll need for my finished harness, but if I have any questions about what something is or where it belongs, I want to be able to definitively place it in the diagrams. Besides, it's just time and tape. Thanks for all your help!!
Hi I dieted the factory harness, starting at the most important component the ECU,then kept the wires in the plugs on the ECU.
Following every wire away from the ECU until it was spliced or terminated, cut it there or removed the pin and labeled the wire connector number and pin, then marked in the wrx wiring diagram wire as removed.
Continue this until only the computer wiring is completely removed. I know about half way into it you’ll think what did I do this for but pick one circuit and complete it. You must have the Subaru diagram in front of you and will learn it intimately!
My theory was I need the engine to turn the back wheels.and the engine electrical is totally on its own. The rest of the car is it’s own also but following the Subaru mentality as to matching the factory drawings. Modifying each circuit in the drawings to match my system. I did follow one of the other builds and installed three relay/fuse blocks from busman.one battery fed and one ignition fed and the other is a combination of both.
Disclaimer here I am an electrician with schematic experience so even I was “whelmed” not over whelmed and was suprised at the ground wiring splices within the harness that the crimps were loose. Can you say wiring gremlins and drive ability issues from the factory harness?
Go slow and label everything and don’t throw away the rest of the harness, you may need a pin or connector.
The last picture is the ferrules I used to splice a wire. Remove the plastic part or get the ferrules without the colored plastic. A wire can go in each side and overlap parallel then crimp with a ferrule crimper, solder, then adhesive shrink tubing.
Here’s a link to the crimper https://www.homedepot.com/p/Pro-sKit...FcvZwAodYHoJbA
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Originally Posted by K3LAG
