Author Topic: Is the Junction block important?  (Read 10819 times)

Offline FOOSE

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Is the Junction block important?
« on: March 27, 2013, 08:36:20 PM »
Hey guys, i'm new on here and i have some wiring questions,

I'm building a custom hotrod 83 chevy short bed  8) and i bought it with the junction block taken off and the wires were all "jimmy rigged" together, so as i re-did the wiring under the hood i made sure they were all hidden (since its a custom truck) i had to lengthen some wires and replaced most of them, i never put a junction block or any fusible links back in.

What are they for? are they important? what do they do? will i have to redo my wiring now????

I've spent hours trying to find answers but nobody seems to know...
Could someone PLEASE help me out?

Thanks a bunch!!

Online bd

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Re: Is the Junction block important?
« Reply #1 on: March 27, 2013, 11:15:08 PM »
Welcome to the site from California!  Sounds like you're putting together a really nice ride.

Show us pics!!   8)

Fusible links are the fundamental, primary protection for the main power busses in the electrical system.  Think of them as slow-blow fuses that protect the main power wires and help guard against electrical fires.  Think of them as proven insurance against your truck burning to the ground in a burst of flaming, radiant glory - house too, should it be parked in the garage.   :o    And, they are really inexpensive!   :)    Fusible links are very important to place at the 'source end' of major wire connections that subsequently split to feed multiple sub-circuits (e.g., the cab feed wires that connect to battery power at the starter), or high-current circuits that otherwise are not protected (e.g., alternator charge lead). 

So, you should use fusible links to protect your ride, but install them strategically and discreetly, so they aren't visually obtrusive.

Junction blocks aren't necessary, but are very convenient to connect multiple wires, especially if wires may need to be added later or to provide convenient locations to attach... fusible links....  Choosing the correct gauge of fusible wire depends exclusively on the gauge of the wire being protected.  For details on adding/replacing a fusible link, go here:  How to make a Fusible Link

So, your hours of research have paid off!  Now, you have your answer....   :D
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline FOOSE

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Re: Is the Junction block important?
« Reply #2 on: March 29, 2013, 01:21:50 AM »
Wow thanks for the quick reply! I'm Canadian so you wanna trade weather?? haha ;D

Well that really helped alot! :) i drew a quick diagram of all the major power wires coming from the battery showing exactly how i wired everything, could you tell me if i messed up on anything?

Also if you could take this image and circle the areas i need a fusible link and repost it that would be super awesome!

Alternator, heater, and starter solenoid wires are all 10gauge, the rest are 12gauge besides the thick starter cable and subwoofer amp cable.


Online bd

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Re: Is the Junction block important?
« Reply #3 on: March 30, 2013, 01:35:02 AM »
I'm afraid this is as specific as I can be, using the information you've provided.

Referencing the colors in your image:
  • Purple (10 Ga) - heater/AC...
    Protect the "Purple" circuit with a fuse link at the battery.  In addition, the control circuits should be fused.

  • Yellow (12 Ga) - ? ? ? ?
    What does the "Yellow" circuit feed?  It needs some form of circuit protection (fuse, breaker, or fuse link - near the battery).

  • Blue (12 Ga) - "fused" battery feed to fuel pump...
    I hope your fuel pump is controlled by a switch or relay.  A relay control circuit should be "fused" separately from the pump motor.

  • Red (10 Ga) - battery feed to cab/alternator/radiator fan...
    Protect the "Red" circuit with a fuse link at the battery.  Optimally, separate the alternator charge lead from the "Red" cab feed and route the charge lead directly to battery on a dedicated wire.  Protect the charge lead with its own fuse link at the battery.  If alternator rating is greater than ~75 amps, or the run is greater than ~8 feet, increase the wire size of the charge lead and its fuse link.  For example: I run a 3-foot-long, 4-gauge charge lead through an 8-gauge link to protect a 140-amp alternator.  If you're powering heavy accessory loads from the "Red" circuit, consider bumping the wire size of the "Red" circuit.  Similar approach applies to the "Yellow" circuit.

  • Pink (10 Ga) - starter solenoid...
    Is the "Pink" circuit powered by the "Red" or "Yellow" feed?  The corresponding feed protection will protect the "Pink" circuit, as well.

  • Green (12 Ga) - distributor...
    Similarly, the corresponding feed circuit protection will protect the "Green" ignition circuit, as well.

General considerations:
  • When installing circuit protection, place it as close to the power source as possible.

  • When stringing new wire, maintain the same wire gauge all the way through the circuit, unless connected sub-circuits are independently fused; in which case the fused sub-circuits can be of smaller wire size.

  • Never pull a wire or harness tight between attachment points.  Always incorporate some slack to allow for movement and subsequent repairs.

  • For any given current load, the longer the wire run, the greater the wire size required to avoid unacceptable voltage loss across the length of the wire.  Some loss is eminent - the goal is to manage the amount of loss.

  • All wire connections to terminal ends or butt-splices should be crimped for a strong mechanical connection, and then soldered using 60/40 rosin core solder for a durable electrical connection.
I hope this helps you.

And, don't forget, we'd love to see pics!
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline FOOSE

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Re: Is the Junction block important?
« Reply #4 on: April 01, 2013, 11:33:44 PM »


It did help me alot! Thank you!  :D

I drew up another diagram of how i'd change the wiring... let me know what you think.

Yes the fuel pump and electric fan are wired up proper with relays...i'm not sure what the red and yellow wires power, all i know is they go into the bulkhead connector and everything else is factory under the dash.

I have a 105amp alternator, i was thinking running a new 8 gauge wire which is about 8 feet long. Is that big enough?

and since there's so many wires leading to the battery, i figured i'd put in a junction block, (shown in the picture) from there i'd only need one wire and one fuse link, what would be the proper wire size for the blue wire going to the battery from the junction block? also what size fuse link?


Offline FOOSE

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Re: Is the Junction block important?
« Reply #5 on: April 01, 2013, 11:48:51 PM »
heres some pics of my project...they're not very clear... :)

Online bd

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Re: Is the Junction block important?
« Reply #6 on: April 02, 2013, 02:56:55 AM »
That's an exciting build!!   :D

When you get a chance, start a thread in Members Rides and keep us apprised of your progress!  It's always enjoyable to watch a major project evolve and come to fruition.  ...motivates the rest of us.   ;)

The following is my opinion and suggestion, and not the only way to accomplish your purpose...
Concerning the charge lead from the alternator: industry views 3% - 5% voltage loss across a wire run as acceptable.  I tend to plan conservatively for ~2.5%.  It's not likely your alternator will output 105 amps for more than 1 - 2 minutes at a time before tapering off 25+%.  With this in mind an 8-ft charge lead anticipated to carry up to 100 amps should be a minimum of 6 gauge, preferably 4 gauge.  A 6-gauge charge lead will require a 10-gauge link, whereas a 4-gauge charge lead will require an 8-gauge link.

Referring to your most recent diagram...
The junction block is a good idea.  However, if the dark blue wire will be less than ~3 ft long, don't bother protecting it beyond, perhaps, wrapping it in convoluted loom.  I would build the dark blue cable out of 4-gauge copper.  (Incidentally, avoid copper-clad aluminum cable, commonly used by GM for battery cable).  Add fuse links to the yellow, red, and purple wires where they connect to the stud.  Here's why: The link used to protect 4-gauge cable is 8-gauge.  The 8-gauge link is larger than the sub-circuit wires it's supposed to protect.  If you experienced an overload, the link wouldn't melt and you would have fire! 

Regarding the red and yellow wires, one probably supplies the headlamp switch, while the other supplies the ignition switch and everything else.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline FOOSE

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Re: Is the Junction block important?
« Reply #7 on: April 12, 2013, 11:03:19 PM »
perfect!  :D

I think i got it all figured out how to change everything now! except the 10 and 12 gauge wires,
what size fuse link do i need for those wires?

Online bd

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Re: Is the Junction block important?
« Reply #8 on: April 13, 2013, 10:10:41 AM »
perfect!  :D

I think i got it all figured out how to change everything now! except the 10 and 12 gauge wires,
what size fuse link do i need for those wires?

Glad to hear you've got it sorted out.

Industry standard is to take the wire gauge you need to protect and add 4 to determine the gauge of the fusible link.  For example, to protect 10-ga wire, use 14-ga link ...for 12-ga wire, use 16-ga link, etc.  Fusible links should be ~6" long, installed at the power source end of the wire being protected.  Good mechanical and electrical connection is mandatory!  Again, take a look here for an example of How to make a Fusible Link.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline Dirty Offio

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Re: Is the Junction block important?
« Reply #9 on: April 15, 2013, 12:43:58 PM »
Foose,

A couple thoughts for you.  I fyou look at the pic I posted, there are 2 things for rewiring.  The clear plastic housing that the battery cable runs into is a MAXI fuse holder.  Maxi's seem to have replaced fusible links in later model vehicles.  (much easier to use!)  Those holders are 6-10 dollars at Walmart in the car stereo section.  The other item to point out is the blade fuse fuse block.  That one is from Bussman, and it has 1 power inlet for 6 fused outlets (get it at AUTOZONE or O'Reillys).  There is another style of these that has 1 inlet and 1 outlet per fuse, that I have only found at AUTOZONE.  (Don't have a pic of that one.)

Just thought i would toss this out so you could consider using them in your build.  The picture is of my old Highboy Ford 4x4, the wiring it it was FUBAR when I got it...after several years, I got pissed and rewired the dang thing.  Took a couple days, but when I was done, everything worked the way it was supposed to and it was quite a bit cleaner too.  I wasn't going for hidden and custom, just functional and relatively clean.

On the MAXI fuse vs. fusible link, if I am wrong about this, someone please correct me.

Cheers folks!

Offio

Offline FOOSE

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Re: Is the Junction block important?
« Reply #10 on: May 03, 2013, 12:46:54 PM »
Ok well everything has been very helpful! but I ran into another problem, i'm not sure if I should start a new topic or just ask you here. bd, you seem to know what you're talking about, so how would you wire up a 5 wire GM alternator?? ???

I bought the March serpentine pulley system and the alternator they gave me has a connector with 4 little prongs.. i'm lost on that one. never heard of a 5 wire before I got this one.

Any help will be much appreciated!!  :D

Online bd

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Re: Is the Junction block important?
« Reply #11 on: May 03, 2013, 02:39:30 PM »
Follow the Nova Resource link in this post by VileZambonie: Alternators
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)

Offline FOOSE

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Re: Is the Junction block important?
« Reply #12 on: May 22, 2013, 08:11:16 PM »
Ok I've been all over my gauge cluster and wiring but I can't find an "idiot light" so I must not have one. I need to hook up the "L" wire to a resister with 35 or more ohms (according to the Nova Resource Link). the idiot light was suppose to give me the resistance so now what?? :-\

Are those resistors available as a wire to just solder in? 

Online bd

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Re: Is the Junction block important?
« Reply #13 on: May 23, 2013, 12:13:53 AM »
Ok I've been all over my gauge cluster and wiring but I can't find an "idiot light" so I must not have one. I need to hook up the "L" wire to a resister with 35 or more ohms (according to the Nova Resource Link). the idiot light was suppose to give me the resistance so now what?? :-\

Are those resistors available as a wire to just solder in? 

The factory typically substituted resistance wire for an idiot light, but, in practice, the wire has proven impossible to procure.  So, use a resistor.

Resistors in a broad selection of values and styles are available from Radio Shack or any local electronic components supply.  Start with a 50-ohm, two-watt resistor installed under the dash between 12-volt ignition and the alternator, per the instructions on the Nova Resource website.
Rich
It's difficult to know just how much you don't know until you know it.
In other words... if people learn by making mistakes, by now I should know just about everything!!!
87 R10 Silverado Fleetside 355 MPFI 700R4 3.42 Locker (aka Rusty, aka Mater)