Painless 20120 Harness Installation

Discussion in 'Classic Mustang Specific Tech' started by geordie, Mar 24, 2008.

  1. This thread will track the installation of a Painless 20120 wiring harness in my ’65 Mustang Coupe. The intention is not to detail the entire installation but rather to highlight some of the problems I ran into, or mistakes I made.
    Let’s just say, before I start, that I’m not an electrical wizard.
    My car is a rolling shell at the moment. The entire dash is stripped out.

    Ok lets go.

    1. Before I started I did examine the contents of the harness kit and verified that I had all the separate parts per the parts list. I also examined all the connectors to verify that they were good. I did this so that there would be no surprises when I got the thing under the dash. This turned out to be a good idea as I found a cracked connector. Rather than return the harness, I chose to replace it.
    2. Drilling the 1.25 inch holes in the firewall for the pass through plates. This wasn’t as easy as it sounds. I used a hole saw, but the task was to open up an existing rectangular hole. There wasn’t any material there for the pilot drill of the hole saw, so I ended up having to screw a block of wood to the interior of the firewall, using some existing holes and use that for the pilot drill.
    3. Installation of the pass through plates on the firewall. Painless do not supply a drill template. My advice would be to make one. In addition for the large square plate, one of the corner holes coincides with the sloping part of the firewall (see attached photo). It was difficult to drill and install this screw. It may have been better to drill another hole in the pass through plate in a more suitable position. Access to drill any holes was very tight on the smaller pass through plate between the drivers fender and the and brake MC. I had to remove the MC.
    4. Painless has advised me that it is easier to insert the harnesses through the pass through plates before the plates are screwed to the firewall.
    5. Installation of the new fuse box base plate was very difficult. The mounting hole pattern is different to the existing fuse box. Painless do not supply an adapter plate. It was necessary to drill mounting holes for the new fuse box under the dash. This was very difficult to access. Again Painless do not supply a drill template. My advice would be to make one.
    6. Finally mounting the fuse box to the mounting plate. Look at the photo in the instructions. The harness is supposed to exit from the top. I was tired and (stupidly) installed mine upside down, it’s not fool proofed. It was a pig to separate the fuse box from the base plate. I had to make a tool to bend the four plastic tabs to allow the two to separate.
    7. Next week I’ll start the routing. I’ll be using Painless Powerbraid sheathing. I’ve already bought a bunch of good quality tie wraps.

    More later. Any other comments from people with experience of Painless Wiring harnesses would be appreciated.

    Attached Files:

  2. Guess there wasn’t a lot of interest in this thread, but I’ll continue with this install.

    1. By making a tool from a bent tip electrical screwdriver I was able to remove the fuse box, which I had incorrectly installed upside down.
    2. I replaced both connectors, male and female, for the steering column to dash harness connection. The painless connectors use a Mohl type crimp pin which needs special crimpers, generally not available in Home Depot, Radioshack or similar. I picked up a pair for about $17 online from Parts Express. These form the pin crimp correctly and worked very well.
    3. I then decided that it would be very difficult to wrap the harness with the Painless Powerbraid, or tape, when it is installed behind the dash. So I started wrapping it outside the car.
    4. I’m using UV resistant tie wraps around the harness bundles every 6 inches, then the same tie warps around the Powerbraid every 2 inches for a neat installation. I’m also cutting a few of the Painless harness tie wraps to allow me to wrap bundles of 8 to 10 wires and then using new tie wraps to reassemble it.
    5. When you cut the Powerbraid the ends need to be fused with a flame to prevent fraying.
    6. I dug out my Mustang wiring harness charts which I starting to understand now a little better. They are also very useful for routing.
    7. The harness does include wire for rear courtesy lights, these were Fastback only. As my car is a Coupe I will be sealing the connectors with heat shrink and bundling them under the Powerbraid. I will be making a list of unused wiring locations in the car so that I could at some future time locate this stuff if I needed to.
    8. The harness does include hazard warning light wiring which I plan to keep but the repro hazard switch is about $190 so I’ll have to find something cheaper than that.
    9. So I am currently trying to identify any more un-needed wiring and completing my bundle wrapping prior to install behind the dash, hopefully this Saturday.
  3. Good writeups. Im going to be installing a painless harness down the line so it's good to have it and I can just search all the info.
  4. I had subscribed to the thread when you first posted. Just don't got any questions or comments at this time I plan on doing my 67 in the future. Nice write up thus far.
  5. Nice write up.

    Been thinking of doing mine soon, would you recommend the painless kit for other mustang guys?
  6. I've put a painless system in my 62 T-bird and my fathers 55 T-bird. Only advice I can offer is don't question the logic of where things go to. Thinking too much got me in trouble on my 62. Other than that, it's pretty straight forward.
  7. I have a painless harness that I am going to install in the 68 so I find this an interesting thread. Keep us posted.
  8. I've wired a few cars in my day. One thing I like to do is route all the wiring so it's hidden. Makes for a cleaner-looking install, especially in the engine compartment area. Ron Francis kits are the best. Don't get discouraged if everything doesn't work right off the bat. There's nothing like re-wiring a car and turning the key that first time and having everything come to life.:flag:
  9. Meee 2

    Is looking to use Painless for my -69.
    But I´ll have to wait a little, just bought new UCA´s from Global West.
    Keep up the good work :nice: and please keep us posted.
  10. Spent another 5 or 6 hours wrapping the main harness (behind the dash) this weekend. It’s about 2/3 wrapped. I’m about 15-20 hours into this project so far. I’ve installed the pass through plates on the firewall, installed the fuse block and the rest of the time has been spent harness wrapping. Painless say to reckon on 40 hours for an install.

    1. I’m applying shrink wrap to every bullet connector and similar.
    2. I’m zip tying each harness bundles every six inches.
    3. Then I’m wrapping the bundles with Painless Powerbraid.
    4. Then I’m zip tying the Powerbraid every 2 inches.
    5. After that I’m re-identifying each bundle.
    6. Where I have a smaller wire bundle joining a larger one, I wrap the small ones first then the larger one with the Powerbraid. I then warp the actual joint with electrical tape. Finally I wrap the joint with a short length of the plastic split wire wrap tubing, zip tied on.

    I ran out of the 0.5 inch diameter Powerbraid sleeving this weekend. I’ve ordered another $100 bucks work. This stuff isn’t cheap.
    I’ll try and post some progress pictures this evening.
  11. another thing you might want to think about (if you are not there yet) is only hook up one thing at a time and test it. that way, if you have a problem, it's quicker and easier to figure out where things went wrong.
  12. After what seems like a lot of work, the dash harness is now wrapped with Powerbraid and all the bundles re-identified and ready to go in the car. I only hope it still fits.

    Attached Files:

  13. Looking good hope that all goes well on the reinstall.
  14. This is a great thread.... as I'm sure alot of guys are in my shoes, with lots of work to do before the wiring phase, but It's gonna have to happen eventually. I've saved these posts in a word-doc ( I hope that's OK) and will reference them when I get to this stage in my '66 coupe. FWIW, I havent found an aftermarket wiring system yet that isnt a tad intimidating..... This prpject requires alot of patience and time, there's no such thin gas a drop in harness that only takes a couple of hours. Panless does have good customer support of you ever get into trouble.

    Thaks for taking the time to write this up.... alot of guys are ghosting this thread... trust me!

  15. x2. Holla.
  16. There use to be ones from painless that were factory replacements. I don't know if they still sell them ($$$). There are also aftermarket reproductions that drop in.

    In general if you are drilling anything, its a good idea to take a punch and dimple what ever you are going to drill into so your bit doesn't walk on you. On a curved surface, a proper dimple makes a world of difference.
  17. I'm back on this project after a couple of weeks off. I wrapped the headlight section 'B' harness in just a couple of hours, now that I've worked my 'system' out, spacing of tie wraps under and on top of the braid, etc. It was a much simpler harness than the under dash harness which must have took me about 15 hours all told.

    My '65 Coupe has been in the shop the last three weeks having the drivers side foot well replaced and some chassis painting done. It's getting towed back to my home today.

    I'm going to wrap the remaining engine harness during the evenings this week, then maybe at the weekend I'll be able to report some new hits and tips on actual installation.
  18. Great thread. These things are not done in five minutes ... please keep this thread going with your thoughts (and lots of pics for the electrically-challenged ie me).

    I plan on doing my 66 fastback with the Painless kit.
  19. I got back to the re-wiring project this weekend.
    I finished wrapping all the three main harnesses, dash, engine and front lighting with Powerbraid.
    I then installed the dash harness in the car. After that I fed the trunk section of the dash harness through the openings in the drivers side door post, along the top on the rocker panel, into the rear drivers side panel and open over the rear drivers side wheel. No issues.
    I then went to install the engine and front lighting section. Now the instructions say to pass the white connectors from each section through the pass through plate grommets. Guys, there’s no way these connector are going to go through these grommets. I even tried warming them up with some hot water :shrug:. I took a tip from a recent Mustang magazine and split the grommets with a razor blade on one side. After that the front lighting harness was installed. However, even splitting the engine section pass through plate grommet was not sufficient, the bundle was too large a diameter, so I replaced the grommet with one from my parts bin. These pass through plate and grommet systems suck.
    I’ve laid out the harnesses in their approximate locations and am about to start making connections at the front of the car.
    I’ll post some new pictures soon.
  20. Subscribed, hopefully I'll be ready to embark on a similar project within the next year :nice: