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65 Mustang Underdash Wiring Project

3K views 19 replies 9 participants last post by  RPOHara 
#1 ·
After many years, I have finally decided to tackle the underdash wiring on my '65. Basically, I am replacing the fuse panel on the driver's side over to the passenger side inside the glove box. I am also going to rebuild the wiring harness from scratch and see how things go. I decided not to go the easy route and just buy an aftermarket harness, etc., because of the cost and I like a challenge or two. I have been keeping the UPS and USPS folks busy with orders coming in for the last couple of weeks.

Here's what I'm starting with:
 

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#2 ·
New Stuff

And here has what has arrived so far. This is just about everything that I'll need to get this project going and finished. I figured while I had everything out from under the dash, I'll replace the two speed wiper system with a delayed wiper system, along with some USB chargers for electronics, a tachometer, and a clock. I just need to clean up the mess now.
 

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#5 ·
While it may seem more solid to solder wires into connectors and cover the joint with heat shrink tubing, numerous studies in the aircraft and marine industries have shown that a proper crimp sealed with heat shrink is far more vibration resistant.

The hard solder to stranded wire does not stand up to vibration.

I spent years soldering and heat shrink tubing and I have stopped...

Marine (Ancor brand) heat shrink infused with RTV is the best you can use to prevent oxidation at the crimp point.
 
#6 ·
16 year Navy Aviation Electronics guy here and I concur as well, polyolefin heat shrink and quality one piece splices are just as good if not better than solder and easier as well.
 
#7 ·
NASA-STD 8739.4...Section 19.1 would disagree with the crimp-is-best theory.
In my work in aerospace we only used soldering, crimping was only for connectors (pins and sockets that went into plugs).
It is very difficult to 'see' if you got a good crimp other than the basic 'tug-on-the-wire' test. Soldering is easier to get correct, it's: lighter, smaller and doesn't require quality tools/crimp barrels to have good success.
 
#8 ·
Okay - back on subject. Here's the wiring harness laid out and taped so I can follow it. Also, pictured is the future panel with relays, IVR, ignition kill switch, and fuse boxes mocked up. The fuse box on the left will be used for those items powered on from the ignition switch, and the right one will be for those items that use a constant voltage supply.
 

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#11 ·
An Update

It was a busy holiday season, and also with the colder weather and a heating system that went out and had to be replaced by me, back on track. Since I work graveyard shift, I only get a couple of hours a day to take care of projects that crop up. I also have to do my work outside (no garage), so as soon as the sun starts to set, I'm done.

Anyways, here's a pic of the back of the instrument cluster. I moved the IVR/CVR to a panel that will go where the glovebox liner used to be, and replaced the incandescent lights with LED's. I also put a couple of multiple wire connectors on each side of the instrument cluster to make it easier to remove when necessary. All the gauges and lights work - so far, so good. :)
 

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#12 ·
Under Hoot Update

Finished the wiring under the hood. Don't mind the dust and dirt...the car sits outside and hasn't been washed in awhile. I figured while I had the wiring all out, I would add some headlight relays. At first the lights weren't all that impressive, and when I turned on the turn signals, the headlights would flash, too. Those darn pesky ground wires - they need to be hooked up. After that, all was well. Back to the inside!
 

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#14 ·
Years ago, I used a more modern voltage regulator, and while running it, the battery wasn't charging. I went back to the stock-type setup, and haven't had any problems since. It's not broken, so.... :) Thanks for the compliment on the instrument cluster. So far everything seems to be working.
 
#17 ·
Lee,


I am contemplating doing the same thing as you for my 66. Where did you purchase the wires, connectors, fuse boxes, and so on? I've had a hard time finding them.


Also, did you use the same style connectors through the firewall as original?


Thanks,


Bob O'Hara
 
#18 ·
I am contemplating doing the same thing as you for my 66. Where did you purchase the wires, connectors, fuse boxes, and so on? I've had a hard time finding them.


Also, did you use the same style connectors through the firewall as original?
Bob - I spent an hour answering your questions, explaining how I did everything, websites, etc, and then when I went to submit it, I get a message that I had to log back in because my session timed out and lost everything. Can't believe it. I will try again in the morning after I wake up :(
 
#19 ·
Hi Bob. Let me try this again.

I started this project by taking a '65 Mustang wiring diagram, and writing down a list of all the colors of wires. I made sure to exclude wires for accessories that I didn't have like AC, and also for the neutral safety switch because I have converted my car over to a manual. I also noted which colors were repeated.
Along with the wire colors, I started figuring out what gauge of wire to go with. I planned on not going with anything smaller than 16 gauge. I used 14 gauge wire for heater control wires, the horns, wiper motor, and power to the ignition switch. I used 12 gauge wire for black/yellow wire that supplies electrical power from the battery to the interior of the car. Everything else got 16 gauge wire.

I measured all the wires with the harnesses out of the car. I used a measuring tape; the kind a seamstress uses to measure around one's body. It's flexibility made it easier to use to follow the contours of the wires. Whatever lengths I came up with, I added another foot just to be on the safe side. Better to have too much wire than not enough.

For the connectors, I spent alot of time online figuring out what I wanted to use. Once I figured what I liked and thought I could handle, I went Delphi connectors. Instead of using the 90 degree angled pigtails on the backs of the gauges, I used two Delphi type connectors on each side of the instrument panel and used nuts to secure the wires to the back of the individual gauges. I bought female connectors and sockets, male connectors and pins, crimping tool, etc., all through Mouser Electronics - Electronic Components Distributor. I liked Mouser because you can buy individual components in the amounts you need instead of getting stuck of having to buy 25 of something when you only need 10.

For the wire, I went through Rhode Island Wiring Service Inc.. They have wire in just about any color combination you would need. You can't order their product online - you have to call and actually talk to a human. I spoke with a guy named Travis, told him what I was doing, and started down my list. I gave him the wire color, tracer color, gauge, and length I needed, i.e., I need red wire, white tracer, 16 gauge, 15 feet. They have a minimum length of 10 feet per color, but that's okay. Better to have too much than not enough, right? Also, speak clearly! I ordered 15 feet of blue/red 16 gauge wire, and got 50 feet of it. Oh well, I'll keep it. If for some reason Rhode Island Wiring doesn't have the color combination you need, another place to check is on eBay. Look for a seller that goes by "brussellex" or "4rcustomswire". I think they are the same operation, but who knows. They sell wire by the foot, and have a chart to show what they have available. The only thing about their wire is that instead of the straight tracer that runs along the length of the wire, it "spirals" around the wire. For example, the wire that runs from the oil pressure sender to the gauge is white with a red tracer. The red tracer spirals around the white, and sort of looks like a candy cane. If one is looking for a concours wiring job, this is not the wire to use.

For the firewall connectors, I reused my old ones. I contacted a company that manufactures the stock-type wiring harnesses for our cars, but they wouldn't sell me the individual connectors because they said it was because the terminals are molded into the rubber blocks and couldn't be replaced. So what I ended up doing was drilling out all but two of the terminals on the connectors and enlarging the holes a little bit to allow wires to pass through. I cut the wires for the two remaining terminals as close to the connector blocks as I could get them. I used these two dead terminals to hold the connectors together while I passed the wires through the holes for the terminals I removed. If someone knows of a better way to do this, I'm interested.

The two fuse blocks I used are Bussmann - one has 6 fuses and the other has 8. I ran the hot wire from the battery into the 8 fuse block. I used that terminal stud to also supply power to the ignition switch, ignition kill switch, and the headlight switch. The 6 fuse block is used to provide power to those accessories in the car that utilize switched-on power, to include the heater motor, wipers, instrument cluster, etc.
 
#20 ·
Lee,


Thank you so very much for the detailed response. Your response has encouraged me to do the same thing as you. While I won't get started until the car comes back from the body shop, I will keep the forum posted with my progress.


Thanks, again.


Bob O'Hara
 
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