69 fuse block

[DougG69]

Ok, having gotten some good advice on testing equipment in another thread, I thought it best to start a new one to ask a few questions about the actual wiring harness itself.

I dug out my spare harness to familiarize myself with it a little since I'm still waiting for the car to get back home from paint (2 more weeks, the paint guy said). When looking at the fuse block, I noticed there was a large opening with a single terminal marked ACCY POST [see arrow (1) in pic below].



It has the black wire with green stripe connected to the back, which according to the wiring diagram should feed from the accessory position on the ignition switch. Could I run a fuse tap there for accessory power? Or otherwise splice into or even re-route the black/green wire to a terminal block if needed?

Also, I noticed an empty space where it looked like a fuse could go, but there were no terminals [see arrow (2) in pic above]. Reading horizontally, below the opening, it says 14A WARN LPS. Reading vertically, along the right side of the opening, it says 14A HEATER. So I guess this is a two-parter:
a) Is there something missing there?
b) If so, is it the fuse for the warning lamps or the heater?

Thanks in advance for any info - Doug

[Midlife]

All 1969's that I have seen have no clips in the area at the bottom of your picture.  Don't forget the fuse box was used across many lines of Fords and Mercurys and across many years.

As for the ACC single clip: notice the slanted empty space?  Another clip plus a hold-down fastener goes in that area that contains a single wire going to a three-prong female connector for ACC plug-ins.  That piece didn't go into every Mustang, but only about 10% of them had it for some reason or another.  Yes, the black/green wire is your ACC line, and you can tap into it if you need to.

Hope this helps.

[DougG69]

As for the ACC single clip: notice the slanted empty space?  Another clip plus a hold-down fastener goes in that area that contains a single wire going to a three-prong female connector for ACC plug-ins.

Thanks for the info, very helpful.

Re: the black/green wire... given what you are saying about the missing clip/prong setup, there's really no reason for that wire to even run to the fuse block at all, is there? IOW, I'm thinking about re-routing it to the area behind the glove box where I would like to organize some group connectors for accessory power, constant power, etc.

In fact, if I hadn't already replaced the headlight harness with a factory style repro, I would be looking to upgrade to a modern fuse block, and probably sticking it behind the glovebox area as well. I would still do it if I could use the factory firewall connector, I just don't know what effect all the splicing & extra length of wire would have. I'm assuming there's a no-no in there somewhere.

[Midlife]

The black/green wire goes to a single point on a triangular buss on the back of the fuse box that allows three different fuses to connect to the main ACC line.  The black/green wire does not go only to that isolated fuse clip.

If you know what you are doing, you can replace the fuse box with whatever you want and wherever you want.  You need to ensure that you do not exceed the load capacity of the existing wiring, or you'll fry the insulation before the fuse blows.  Even with Ford's design, I see about 20% of all harnesses have burned insulation due to shorts.  I cannot vouch that fuses were installed when the fire began, but I do see the results...

As for relocating the fuse box, you might as well start with Painful, Ron Francis, or similar after-market wiring kits.

[DougG69]

The black/green wire does not go only to that isolated fuse clip.

That should have been obvious to me if I would have thought about it at all before I posted...

If you know what you are doing, you can replace the fuse box with whatever you want and wherever you want.  You need to ensure that you do not exceed the load capacity of the existing wiring, or you'll fry the insulation before the fuse blows.

I'll need to do quite a bit of studying on the wiring diagrams before getting comfortable enough to begin a project of this magnitude. I would like to make sure I understand the factory harness first. I think it will be helpful to have a spare harness out of the car to refer to.

As for relocating the fuse box, you might as well start with Painful, Ron Francis, or similar after-market wiring kits.

I have been looking at a few options, including those. Painless is running a $100 rebate offer through the end of July, but that still doesn't make it cheap. The Ron Francis 24/7 kit really appeals to me in that it can be pulled out from under the dash to where you can get at it easily. I have also been looking at Centech. Do you have any experience with them?

[Midlife]

I did a little bit of follow-on work on Laurie's car with Painful.  The only good I saw was that each wire was clearly labeled for its application.

Personally, I find all of these aftermarket kits too expensive for my taste.  Of course, I have access to 100+ used harnesses and could create anything I needed out of them for my own use.  There's probably only a dozen of us with that inventory in the US though.

[DougG69]

Personally, I find all of these aftermarket kits too expensive for my taste.

Amen. If Painless had a 50% off sale, I'd probably still be too cheap to buy one of their harnesses. I'm sure they are nice though.

To be honest, I would be perfectly happy with the stock underdash harness & just adding an auxiliary fuse panel for extra goodies... until the first time I had to squirm under the steering wheel on my back in the wrestler's bridge position and try to pry one of those glass fuses out :o  Then I would be kicking myself for not going the extra mile when I had the chance.

All I really want is modern blade fuses that can be reached without major contortions. It'll be a lot more work for me if I don't go with one of the big kits, but that's to be expected. Of course, I reserve the right to wimp out and just stick with the stock wiring :-)

[DougG69]

Ok, I've been able to put in a little more time studying the factory wiring diagrams.

It looks like there are only 2 fuses on the 'constant hot' side of the block, fed by the black wire with the yellow stripe. One for the emergency flashers, and the other for the cig lighter and the door switches (that feeds all the dash/courtesy lights).

The headlight switch & the ignition switch are also constant hot, but are not fused. The headlight switch does feed a wire (blue/red stripe) through the fuse block for the interior lights as well.

The 'accessory hot' side of the fuse block also holds 2 fuses (3 if you have the accessory post, which mine doesn't). Fed by the black wire with the green stripe. One fuse for the heater. The other for turn signals, back-up lights, wipers, radio, and the gear selector lamp (for automatic trans).

Any corrections would be welcome. I just want to make sure I have it right.

[Midlife]

Well done, sir! 

Actual battery power comes through the main firewall block, and there's a couple of ACC- or RUN-only lines that go back out, primarily to the Voltage Regulator.  There's another ACC line that goes to the CVR on the dash, but you got the most important lines outlined (pun intended).

[DougG69]

Sweet! Now I'm getting somewhere. Thanks for the confirmation.

BTW, would you happen to know off the top of your head what gauge most of the underdash harness wiring is? I'm stuck at work right now, trying to work out some details on an order. Err, I mean working hard for my employer :-)

[Midlife]

16 gauge for most wiring, except for the main Power and ACC lines, which are 12 or 14 gauge.

[DougG69]

16 gauge for most wiring, except for the main Power and ACC lines, which are 12 or 14 gauge.

And once again, I thank you.

I have been considering a few approaches to this project. On one of the sites where I was doing a little reading, someone mentioned that instead of individual relays for each accessory added, he opted to use a continuous duty solenoid for his switched power. This idea really appeals to me for the sheer simplicity. Is there any reason I shouldn't use a CDS like, say, this one?:

http://www.jamestowndistributors.com/userportal/show_product.do?pid=10170&familyName=Cole+Hersee+85A+Continuous+Duty+Solenoid

It's rated for 85 amps. Do you think this would be able to handle power windows (most likely nu-relics), a 15 amp radio, power antenna, and possibly power door locks?

Or, maybe this bad boy for a little headroom:

http://www.jamestowndistributors.com/userportal/show_product.do?pid=10169&familyName=Cole+Hersee+Continuous+Duty+Solenoid