[no1dc]

With all the additional electrical devices we add to our car would adding an additional power attachment source be okay? What I'm saying is with the fans, headlight upgrades, stereo equipment, etc... we add to these cars instead of trying to get everything hooked up to the horn relay bus bar(as that's where the alt "senses" voltage drop) what about adding an additional terminal block off of the bus bar that one can attach all these addtional electical components to? If one was to do something like that what size wire would you run from the horn relay to the added terminal block? I think locating the block anywhere from 1-2 1/2 feet from the bus bar would be about right to make it accessible. TIA Pete

 

[John_Muha]

How about something like this terminal block? Late 70's Chevy pick-ups used something similar that mounted on the firewall.
http://www.madelectrical.com/electricaltech/remotevoltagesensing.shtml

 

[70ElkySS]

Don't wanna' hijack the thread, but this brings up a question I've had for years.

John, I noticed on that page that they recommended fusible links on all wires leaving the junction. Why would you want fusible links instead of fuses when fuses would be easier to replace if you had a problem?

Thanks!

 

[vrooom3440]

...John, I noticed on that page that they recommended fusible links on all wires leaving the junction. Why would you want fusible links instead of fuses when fuses would be easier to replace if you had a problem?

That borders on a religous question.

You are entirely correct in that a fuse is easier to replace, probably easier to troubleshoot, and much more common and available. The downside of fuses is that they do not tolerate momentary over currents very well. For example my electric fans have an internal resistance of about 0.25 ohms leading to a startup current of 60 amps. Now this current does not last very long as once the fans come up to speed they draw only 15 amps. So using a fuse you need a 60 amp fuse and 60 amp wiring which is way overkill for the normal draw of 15 amps.

The fusible link on the other hand deals with momentary surges like this very gracefully and is only triggered by constant over current. The downsides of the fusible link are much the opposite to fuses with the addition of being a potential ignition source when they blow.

There is also another alternative and that is the circuit breaker. GM put one of these on our cars but built it into the headlight switch (which is why they will sometimes blink). The advantage of the breaker is the potential to be reset when the over current condition has been "fixed".

I believe that MAD also discusses fuses versus fuse links on their site although with the volume of great stuff they have I do not remember exactly where.

Now getting back to the original topic...

I have done something much like you are asking about. I sourced a "distribution box" from a later Ford Taurus and mounted it up on the DS core support in my '68 El Camino. I made a contoured bracket that uses original factory core support holes from the regulator and horn relay to mount it and it hides and just about looks like it belongs there.

The beauty of my solution is that I have loads of additional maxi sized bladed fuse slots to hang stuff off of *and* several (like 7 or 8) relay sockets to deal with horn, headlight high, headlight low, fan high, fan low, and whatever else I come up with. I even have a few regular sized fuse slots plus a 175A maxi fuse in the box. I think I hung the original fuse panel off of a 60A maxi fuse. I have maxi circuit breakers on the headlight relay power supplies.

I used a pretty big hammer on this problem, but a smaller setup could use one of the 4 or 6 fuse weather proof fuse panels as an expansion panel. With these you are pretty much limited to 30A per circuit and 60A (or something like that) total. There are wire current/size charts out there to specify what wire size you need to feed the panel with.

Steve

 

[1Fast7D]

It depends on what you plan on running off the additional terminal block. To be on the safe side just use 8g. For a additional terminal block to add a few items the one John M or the one I posted will work fine. If you plan on adding lots of stuff a "distribution box" out of a late model like Steve used will keep the relays and fuses in one spot.

 

[no1dc]

Greg what I'm wanting to do is clean up my horn relay bus bar that currently has the original three wires attached to it AND two relays for the headlights, a 6 ga from the high amp alt, a 4 ga for the future stereo amplifier.


My thought was to use a 6ga "jumper" from the bus bar to an addtional distribution/terminal block that has male spade ends or bolts and re-attach the add ons from the bus bar to it. Thought it might clean up the area around the bus bar and help make future diagnosis(hopefully not needed, but...) and expansion easier.

Just a thought. TIA Pete

 

[vrooom3440]

Pete,

Sounds like you are really close to needing the distribution box with the number of circuits and the relays too. It can make for a very clean setup if you meet the other requirements like no external voltage regulator.

Steve

 

[no1dc]

Steve the car was converted to internal voltage regulated alt this weekend, or at least wired, waiting for the alt. What distribution bow would you recommend. I'm thinking about going to the slavage yard and getting one out of a newer car that maybe has relays, etc.... Ah the possibilities are endless, just wish I knew what I was doing! Thanks Pete

 

[vrooom3440]

Pete,

I really like the box in the later roundy Ford Taurus for using standard fuses and relays, a relatively compact size, and easier mounting. You may also find the same box in a Ford Explorer. These boxes are of course up under the hood and be sure to get the mounting bracket and a good length of wiring harness too. You will want to graft onto the fuse/relay terminal wires since I have not found a source for new terminals to fit the box. I strip a 0.25"-.5" of the two wires, overlap them, wrap the overlap with a strand of copper wire, and solder the joint. I cover that with one or two layers of heat shrink tubing. For extra credit you can get the heat shrink with glue inside to completely seal the connection.

A lot of the imports use strange and unique fuses and relays so I rule them out. A lot of the boxes hold only fuses so they are not as interesting. A lot have odd shapes.

Note that the Ford box is actually a bit modular. There is a fuse section and three cells that hold the relay modules. I have seen three types of modules: 2 of the regular Bosch 5 terminal relays, 3 of the micro Bosch relays, and a combination. You could get alternate modules and mix and match if you want. There is some dependency on module configuration and the lid however - the lid has ribs that go over module fuse slots to make sure the fuses do not vibrate out. But these ribs can be broken out if you need/want something else there.

Steve

 

[GarageTime]

On the fuse vs. fusible link question, as M.A.D. explains it extremely well in his basics book (well worth buying!), the fuse is a connection in the wire and these connections provide some resistance, where there is resistance there is heat - this is fine if you only have the power on for a short duration (like directionals or brake lights). If it is something like a stereo that is on for extended time there will be heat build-up and as the heat increases so does the resistance and as the resistance increases so does the heat and so on...it is called thermal runaway. With the fusible link you will crimp and solder the ends to virtually eliminate this issue.

 

[John_Muha]

On the fuse vs. fusible link question, as M.A.D. explains it extremely well in his basics book (well worth buying!), the fuse is a connection in the wire and these connections provide some resistance, where there is resistance there is heat - this is fine if you only have the power on for a short duration (like directionals or brake lights). If it is something like a stereo that is on for extended time there will be heat build-up and as the heat increases so does the resistance and as the resistance increases so does the heat and so on...it is called thermal runaway. With the fusible link you will crimp and solder the ends to virtually eliminate this issue.

Ok, but I wouldn't use a fusible link inside a car nor would I use it on a stereo. A fusible link is too slow to react to protect a modern stereo nor would I want something under the dash that burns open. Just my opinion.

 

[vrooom3440]

On the fuse vs. fusible link question, as M.A.D. explains it extremely well in his basics book (well worth buying!), the fuse is a connection in the wire and these connections provide some resistance, where there is resistance there is heat - this is fine if you only have the power on for a short duration (like directionals or brake lights). If it is something like a stereo that is on for extended time there will be heat build-up and as the heat increases so does the resistance and as the resistance increases so does the heat and so on...it is called thermal runaway. With the fusible link you will crimp and solder the ends to virtually eliminate this issue.

This is true to a point in a simplistic way. Reality is usually not so simple.

Heat as a result of resistance depends highly on current flow. At lower current flows there is relatively little heat. As currents increase so can the heat factor. But even that can be ok depending on the ability to radiate the heat. For example the current carrying capacity of a wire is less when the wire is bundled with other wires.

You will note that part of the difference between modern fuses is the size of the terminal tabs. Smaller tabs are used on low current styles and larger tabs on high current styles. This is to reduce resistance on higher current circuits.

Personally I do not want flame or ignition sources anywhere near my car, inside, outside, nor especially under the hood. This is why there are other alternatives to the fuse link. Like Maxi fuses with larger terminal blades and Mega fuses that bolt in with large tabs.

Steve