A muddy resistor bypass - overkill is a GOOD thing!

[MarcusOReallyus]

Well, I finally got around to doing the resistor bypass and put in a new relay while I was at it. Truck's been hard starting, so I figured it was time. Still has the same GPs that were in it when I bought it, so they need to be changed out, too. I have GPs on order. Well, actually, I have GPs around here somewhere that I bought a few months ago, but I have searched high and low and can't find them. As soon as I get a new batch here and installed, the others will show up, of course.

I decided to do mine a little differently than the standard recommended method. I just don't like the idea of putting that GP load on the existing 12v block on the firewall. Yeah, yeah, I know, it works fine for a ton of people who have been running that way for years. I know that. Still, I don't like the idea, so I had some custom cables made to carry the load. We had an interesting discussion about how much current they draw a while back, and Antennaclimber measured it at 80 amps.

I decided I want that 80 amp load running on its own circuit with heavier wire, protected by a Mega fuse. I had the cables made by BestBoatWire.com, and I am VERY pleased with the results. Well, except for the color. The cables are more pink than red! Kind of a salmon, really. Oh well, they fit in with the faded red stock wiring that's there!

Anyway, the quality looks excellent, and the service was great. They forgot to send me an email saying it had shipped, and late one evening I emailed and asked when I could expect my order to ship. I got an email back in a half hour saying that tracking showed it had been delivered. I checked, and sure enough, it had arrived that day in the mail. It was sitting right there, but I hadn't noticed it.

When I took the resistor off I found a bit of a mess. I don't know if this is gen-yoo-wine Iraq mud or what. It's like cement! I found a bunch in one of my alternators, too, but that's another thread.

Anyway, the photos show the results and a bit more work I need to do. Check the circled area in the first photo. I need to clean up some connections, too.

I used 4 gauge from the battery to the fuse block, because I may want to add some accessories there later. I used 6 gauge from the fuse to the GP relay. This is overkill - 8 gauge probably would have been fine, but the price difference was trivial, so I went big.

Speaking of prices, the cabling cost me a whopping $25, shipped. Works for me! The fuse block was $20, which I thought was a bit steep.

To connect to the battery terminal, I replaced the existing 5/16" bolt with a longer, Allen head cap screw, in stainless steel. While I was at it, I did the same for the other terminals, but in standard length. As you can see from the photo, I could probably trim some off.

All the connections got a thin coat of dielectric grease, and I don't expect to have any trouble with this circuit for a loooong time to come.

 

[doghead]

I'm surprised you did not connect directly on the front battery positive cable, to lessen the load on the inter battery cable.

When I redid my battery cables, I actually moved the 12v wire(smaller one) to the front battery terminal, for this same reason.

 

[gimpyrobb]

Looks great! Any reason you went with a fuse instead of a breaker? I have found that the breakers are actually not much more and cheaper in the long run.

 

[MarcusOReallyus]

Gimpy, I didn't find any breakers in that size that were reasonably priced. I would have preferred a breaker.

 

[gimpyrobb]

Fuses of that size are often expensive. If it ever goes, a quick google search for 80amp 12v breaker found this:

http://www.amazon.com/IMC-Audio-AMP-Circuit-Breaker/dp/B007AV5RXM

 

[doghead]

That style CB is used in many modern boats also.

 

[antennaclimber]

Minor correction, it is 100 amps that 8 AC60's draw at 11.3 VDC.

We use these 100 and 150 amp breakers in vehicle radio installations.
http://www.delcity.net/store/Hi!Amp-Surface-Mount-!-<br>Manual-Reset-(Switchable)/p_193073

 

[Recovry4x4]

I did my one of my trucks in 6GA all the way to the front battery. Can't remember which truck. 6GA isn't easy to find at parts houses but the local West Marine had tons of it. When I need top shelf cabling and accessories, I bite the bullet and head to West Marine.

 

[tim292stro]

I don't like breakers for these circuits, breakers can fail shorted negating their purpose.

Fuses of that size are often expensive. If it ever goes, a quick google search for 80amp 12v breaker found this:

http://www.amazon.com/IMC-Audio-AMP-Circuit-Breaker/dp/B007AV5RXM

Another quick search found this: http://www.delcity.net/store/MEGA-Fuses/p_800374.h_800375.t_1.r_IF1003
Average cost for a mega-fuse is $4.50. He could blow about 4x with his existing system before he equals the cost of tearing it out to install a breaker.

One other comment, an area that you can improve MarcusOReallyus, that short stub of wire between the battery and the fuse (great that it appears to be within 18" of the battery connection) you have it zip-tied to a ground point - I'd recommend either wrapping the wire or the metal rod with a slit and glued -on piece of rubber, a wire dressing kit, or a double-plastic-stand-off:


That short but un-fused segment of wire potentially rubbing and shorting (even with the zip-tie) is my only obvious concern with your change , otherwise good work!!

 

[maddawg308]

Great update work on the CUCV electricals, subscribed so I can refer back to this in the near future...

 

[rsh4364]

For power/ground cable I use kolossus fleks kable sold by knuconceptz.com Really nice stuff,I also bought a crimping tool so I can make my own cables.Great thread gonna look into the fuse idea,instead of fuseable links.

 

[mikev]

Well, I finally got around to doing the resistor bypass and put in a new relay while I was at it. Truck's been hard starting...

So, after the work done - does your CUCV start up better?

On my three "hard starting" CUCVs:

* 1986 M1031 SECM was a bad fuel return check valve

* 1986 M1009 was a leaky fuel filter base

* 1984 M1009 was a weak glow plug relay with some bad cable connections/terminals

 

[rsh4364]

what size fuse would you use for power to 12v port?Using 1/0 ga. or 4ga.?Power to GP solenoid would be separate.

 

[MarcusOReallyus]

Minor correction, it is 100 amps that 8 AC60's draw at 11.3 VDC.

Uh, yup. Thanks for the correction. I was going from memory. I did remember we tossed around 120 or 150 amps for circuit protection. I went with 150 for this, as I want some headroom for possible future accessories off that same fuse. I will run a separate cable to a new fuse block if I do that.

I don't like breakers for these circuits, breakers can fail shorted negating their purpose.

Another quick search found this: http://www.delcity.net/store/MEGA-Fuses/p_800374.h_800375.t_1.r_IF1003
Average cost for a mega-fuse is $4.50. He could blow about 4x with his existing system before he equals the cost of tearing it out to install a breaker.

Yep.

One other comment, an area that you can improve MarcusOReallyus, that short stub of wire between the battery and the fuse (great that it appears to be within 18" of the battery connection)

That's exactly 18". That's what I ordered.

IThat short but un-fused segment of wire potentially rubbing and shorting (even with the zip-tie) is my only obvious concern with your change , otherwise good work!!

Yes, that is a weak point. That part is temporary, as I'm not completely happy with the routing there.

For power/ground cable I use kolossus fleks kable sold by knuconceptz.com Really nice stuff,I also bought a crimping tool so I can make my own cables.Great thread gonna look into the fuse idea,instead of fuseable links.

I saw that on Amazon, but other people have the same stuff, and other people don't act like pre-teens with deliberate stupid misspellings.

Well, I finally got around to doing the resistor bypass and put in a new relay while I was at it. Truck's been hard starting...

So, after the work done - does your CUCV start up better?

Dunno yet. I pulled both alternators to rebuild them, and that job isn't done yet. Long story, for another thread. Let's just say the one that looked barely broken in so didn't get rebuilt, now has to be pulled and rebuilt.

I plan to finish that up and replace the GPs next Saturday, then I'll find out!

 

[MarcusOReallyus]

what size fuse would you use for power to 12v port?Using 1/0 ga. or 4ga.?Power to GP solenoid would be separate.

Fuse size depends on what you plan to run on it. That is where you start sizing a circuit - what are the demands?

If you mean the 12v port on the firewall, I woudn't run anything that needs 1/0 ga. or 4ga off that little port. I'd install something bigger.

 

[tim292stro]

Fuse size depends on what you plan to run on it. That is where you start sizing a circuit - what are the demands?

If you mean the 12v port on the firewall, I wouldn't run anything that needs 1/0 ga. or 4ga off that little port. I'd install something bigger.

What he said with minor edit - fuse size depends on wire size. Fuse is ALWAYS to protect the downstream wire length. Wire size is determined by what you want to run off it AND how far away it is from the power supply. Every time there is a wire size reduction or a branch to multiple loads, another fuse is required within 18" of the size-change/branch to protect the new run. Fuses on devices protect the devices, but only if the manufacturer put that in.

Battery size is determined by start requirements plus engine off accessory run time requirements, there are equations and standards to follow for this.

Alternator size is determined by the engine run interval + total loads, both recharging the batteries inside the engine run interval, and running all accessories while the engine is running plus 15-25% margin.

 

[rsh4364]

For power/ground cable I use kolossus fleks kable sold by knuconceptz.com Really nice stuff,I also bought a crimping tool so I can make my own cables.Great thread gonna look into the fuse idea,instead of fuseable links.

And yes,I was really embarrassed to write down their info,Im 50 ,but do like their wire.And battery terminals kbt 30n and kbt 30p

 

[rsh4364]

Fuse size depends on what you plan to run on it. That is where you start sizing a circuit - what are the demands?

If you mean the 12v port on the firewall, I woudn't run anything that needs 1/0 ga. or 4ga off that little port. I'd install something bigger.

my headlights and off road lights on separate circuit,12v port just running the normal,maybe I should run 4/0 gauge?

 

[tim292stro]

I think they mean, the feed to that port is not sufficient to do anything high amperage, so you shouldn't run anything high amperage from it - if you're talking about re-wiring the feed to that 12-port, you might want the scrap more of the OEM electrical in the first place...

I prefer tinned marine wire for my vehicles, a little more expensive, but lasts longer.

 

[MarcusOReallyus]

What he said with minor edit - fuse size depends on wire size.

Which depends on demands, right?

That and distance, of course.


My point is, we don't start by picking a wire size, we start by understanding what the circuit requires. Until we know what it's going to run, we shouldn't even be talking about wire sizes.

my headlights and off road lights on separate circuit,12v port just running the normal,maybe I should run 4/0 gauge?

The existing wire is PLENTY adequate for the stock load. I wouldn't change it at all, if it's running stock load. Since you've put the headlights on a separate circuit, the stock wiring is already overkill. 4/0 would be a complete waste. If you want to replace the fusible link, that's probably not a bad idea.

I were replacing the stock cable to that 12v block I'd probably go with 8 gauge, which is overkill. No way would I go bigger than 6. It would just be a waste. Think about it - I just ran 6 gauge to feed my glow plugs, which are a 100 amp load. Most people doing the bypass just connect to that 12v port, and it works just fine. That means that stock OEM wire is capable of handling that 100 amp load without any problem.

You aren't going to run that extra 100 amp load. In fact, you've taken the headlight load off of that circuit.

I can't think of anything short of a starter, a winch, or a large bank of aircraft landing lights that calls for 1/0 on a vehicle. I like oversizing wire, but only to a point. My 6 gauge for the glow plugs is more than necessary, but only by one gauge size or maybe two. My 4 gauge to the fuse block could easily have been 6 gauge, too, and it would have been perfectly fine. I went up to 4 because it was 50 cents more, and maybe I'll want to put more load on that someday.

On 4WD forums I see a lot of kids using massive cables for no reason. I think it's a "mine is bigger than yours" kind of thing. There's no good reason for it. There is no benefit to it. It's just wasted money and work.

Manufacturers make things as big as they absolutely must, but not one bit bigger. Oh, they do allow an adequate safety margin, but they don't go overboard. Why? Because it all costs money. That 50 cents extra for the 4 gauge feeding my fuse is nothing to me or you. Multiply that by 150 million vehicles, and now you are talking some serious money.

That means that we hobbyists can, in some cases, improve on OEM. We can go beyond "adequate" to "very good". I like to go that one bit bigger than the manufacturer, or sometimes two bits bigger, but I don't want to be ridiculous, and I don't want to throw money away for no benefit. "Mine is bigger than yours" doesn't really mean anything to me. I just want my stuff to work well.


So, bottom line is, I wouldn't change the feed wire on that 12v port. You've already unloaded the headlights from it - there's plenty there for anything reasonable like a stereo (not a big amp) or a CB radio.

If you are going to run something that requires more current, run that separately.