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1968 Camaro LS3 TH400
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Discussion Starter · #1 · (Edited)
Brief preface.
Battery is relocated to the trunk
Current carriers run to the starter and engine block, with 225 amp fuse.
4 gauge from the alternator back to the starter with fusible link
Multiple ground straps to core and body.
10 gauge double lugged from the starter to the original single terminal on the core support.
I have concerns about how to feed this controller to the Mark VIII fan rated at 35 amps…I think
Would you use
1.the terminal on the passenger side that feeds the main 10 gauge harness ?
2. Double off the horn relay, because of controller location?
3. Feed from the alternator?
Would you be concerned about the spike in voltage off the alternator if #3 was used?
This is obviously not in my skill set.
Any help is always appreciated!
Pic won’t help much but the controller will be in the wasted air off the fan
( instructions state the intensional placement is inside an aluminum shroud, and called the mounting bracket a heat sink …..so it got placed in the fan discharge path. Use with a plastic shroud states placement to be on the core support)

278125
 

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I am sure the PWM controller instructions tells you to hook the power wire directly to the battery. It seems like all aftermarket electronics instructions say this. The reason they say this is because the battery acts like a filter. It cleans up the DC waveform and this is the quiet spot in the electrical system. Electronics hate voltage spikes and sags and noise.

The absolute best way is to run a wire from the battery in back of your car to the controller in the front of the car. This is not very practical and ridiculous.

You need to find a spot to connect that does not have voltage spikes and noise in the DC circuit.
1. Do not connect to the alternator. The alternator voltage waveform has little humps in the voltage waveform. Your controller would hate the humps.
2. Do not connect to the starter. If you run your car and stop it, the fans might continue to run until the radiator cools down. If you jump back in the car and start it while the fans are running, there will be a large voltage drop from the current demanded by the starter and the fans. Electronics do not like voltage sags. When the starter stops turning, then you got a voltage spike.
3. You need to wire the controller far away from the alternator and starter. Look at your wiring. Look to see which point is convenient and furthest from these two devices.
4. Do you have a computer controlling your engine? If so, where did you connect the computer?
5. Make sure you add a fusible link or fuse to this wire.
 

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Ridiculousness aside, since you didn’t install a battery stud style terminal under the hood I would be tempted to run a good sized wire back to the battery for the fans. Fans need full voltage and I don’t see a suitable place to find that based on your description.

As you can see, opinions will vary on this. Patrick John aka PJ is a pretty smart fellow so keep that in mind.

Don
 

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1968 Camaro LS3 TH400
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Discussion Starter · #4 · (Edited)
Is TP Smith PJ?
I had just read something he had written about inverse induction…not within my purview either.
Yes ECU controller and is run clean and dedicated to the battery on non discrete posts.
I did run a non discreet 10 ga to a distribution bus , with fused values as recommended. These are sources for constant voltage demands of the Dakota digital,and bus interface module, but I don’t think 10ga will support the fan demand for 15 feet.
so I’m back to where to hide another wire.
I didn’t plan to fail with this, it’s just a failure to plan accordingly….but the PWM fan control was an after thought.
 

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Another question.
Is a capacitor applicable in this instance?
I think it would have to be huge electrolytic capacitor so not really a practical solution imho. Maybe someone has done the math.

Yes PJ is Patrick is tp_smith is John Jones….

Don
 

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1968 Camaro LS3 TH400
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Discussion Starter · #7 ·
Thanks Don!
I looking at ratings for approximate length of 15 feet of 8 gauge….what is your opinion?
or should I run 4 since I obviously don’t have a definitive plan beyond this component.
What are guys with power seats and heated seats doing for power distribution. I know it’s tangental to this discussion…just wondering.
 

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I think that should be ok.

I don’t know about other guys but I bring the large battery cable to a stud in the engine bay. From there to the starter, alternator, fuse block, fans etc. This seems to work well for me and I’ve done it on several cars. I think GM does the same thing on their Camaros with trunk batteries. In fact I buy their battery cables from wrecks on eBay for around $50. A real deal imho.

Don
 

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1968 Camaro LS3 TH400
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Discussion Starter · #9 ·
Well that would have been handy information when I was spending all that time covering cables in two layers of heavy heat shrink, stabilized at bulk heads with high temp epoxy, I obviously didn’t do enough research/planning. I just overlooked the main distribution point.
Thank you Don and TP Smith for your knowledge and guidance.
 

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Well that would have been handy information when I was spending all that time covering cables in two layers of heavy heat shrink, stabilized at bulk heads with high temp epoxy, I obviously didn’t do enough research/planning. I just overlooked the main distribution point.
Thank you Don and TP Smith for your knowledge and guidance.
There are many ways to skin this cat. They all have their merits. No single answer is correct.

Don
 
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Maybe the word ridiculous was too strong of a word. It is a lot of trouble to run a power cable from the back of the car to the front. I hated the idea of having you run another one.

I have a battery in the trunk like you. I ran a 1/0 cable in conduit along the wheel house and along the top of the rocker. The wire exits out the bottom of the firewall where the subframe bolts to the body. At this point, I have a power distribution block. The starter wire is connected to the block and other smaller wires. In the future one of the smaller wires will be the PWM fan controller wire.

The reason a large 1/0 cable was selected was because the starter requires a lot of current. When the starter is not being used, the cable is way oversized. An oversized cable is good because it has a very low impedance path between the battery and the power distribution block. I am able to take advantage of the low impedance (resistance) of the 1/0 cable and connect a PWM fan controller to the distribution block on the firewall. The huge cable makes it almost like connecting directly to the battery.

A capacitor can be added to the front end of the controller. It would have to be huge (0.5 Farad) like Mr. Don mentioned. I would add a capacitor as a last resort.
 

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1968 Camaro LS3 TH400
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Discussion Starter · #12 ·
I looked at the math on capacitor applications, and it’s far more complicated than I expected, and to that point, I clearly see it’s not an option that looks even remotely feasible.
I did read quite a bit about how to route. I considered a conduit and looking at the possibility of hazards from all aspects. I ran through the rocker panel…. I did cover the cables in two layers of thick industrial heat shrink. I even mocked up a piece and did a hillbilly abrasion resistance test with a wire wheel, and a razor knife….not to terribly scientific but it satisfied my curiosity. I did , at least, get the size correct…
I’m considering the first suggestion of a separate cable. That would support what I didn’t consider…like power seats. I’m not sure that I will, but I’m certain there is not adequate supply for existing devices.
I suppose I could go back and redo the main cable as a single terminal from which to distribute.
I even thinking about scraping the relocation and going back to the front with the battery.
 

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I looked at the math on capacitor applications, and it’s far more complicated than I expected, and to that point, I clearly see it’s not an option that looks even remotely feasible.
I did read quite a bit about how to route. I considered a conduit and looking at the possibility of hazards from all aspects. I ran through the rocker panel…. I did cover the cables in two layers of thick industrial heat shrink. I even mocked up a piece and did a hillbilly abrasion resistance test with a wire wheel, and a razor knife….not to terribly scientific but it satisfied my curiosity. I did , at least, get the size correct…
I’m considering the first suggestion of a separate cable. That would support what I didn’t consider…like power seats. I’m not sure that I will, but I’m certain there is not adequate supply for existing devices.
I suppose I could go back and redo the main cable as a single terminal from which to distribute.
I even thinking about scraping the relocation and going back to the front with the battery.
If it were me I would add the stud/ terminal block under the hood and connect everything to it. Alternator, starter, fans etc.

Don
 

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Tim - The Northwest 1969 Camaro
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I think that's essentially what I did. When you have every supplier wanting a direct to battery connection I just moved that connection to the front with a stud on the firewall. I essentially did what Don suggests and either mounted items directly to the stud or ran another heavy gauge wire to another stud under the hood.
 

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1968 Camaro LS3 TH400
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Discussion Starter · #15 ·
I’ll have to look into this bus option.
I sure wish I had thought ahead on this.
Thank you all for taking time to clarify.
 

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I think that should be ok.

I don’t know about other guys but I bring the large battery cable to a stud in the engine bay. From there to the starter, alternator, fuse block, fans etc. This seems to work well for me and I’ve done it on several cars. I think GM does the same thing on their Camaros with trunk batteries. In fact I buy their battery cables from wrecks on eBay for around $50. A real deal imho.

Don
I’ll have to look into this bus option.
I sure wish I had thought ahead on this.
Thank you all for taking time to clarify.
Hey All. The car I bought had a battery in the trunk. The car's pretty much a blank slate. I thought about putting the battery under the hood, but this conversation is making me rethink it. Beyond saving space under the hood, iyo what are the advantages/disadvantages to having the battery in the trunk? Do you have a pic or two of your set up with the battery in the trunk and the studs with terminal block on the firewall?
 

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I think that's essentially what I did. When you have every supplier wanting a direct to battery connection I just moved that connection to the front with a stud on the firewall. I essentially did what Don suggests and either mounted items directly to the stud or ran another heavy gauge wire to another stud under the hood.
Shannon4570 has a nice photo in his build thread of the power distribution block he used. It is a single stud that is mounted low on the car.

If you ran your big cable directly to the the starter, you have enough cable to work with to mount a distribution block in the same area as Mr. Tim.
 

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Discussion Starter · #18 ·
Hey All. The car I bought had a battery in the trunk. The car's pretty much a blank slate. I thought about putting the battery under the hood, but this conversation is making me rethink it. Beyond saving space under the hood, iyo what are the advantages/disadvantages to having the battery in the trunk? Do you have a pic or two of your set up with the battery in the trunk and the studs with terminal block on the firewall?
Your ahead of the crowd just by asking.
I THOUGHT I had read enough about current carrying conductors, the factors that affect voltage drop, over current protection, but I didn’t plan to add electrical components that are sensitive to other factors at the last minute.
Smith is correct….these devices ( PWM and the like)
want clean noise free supply. If you violate that requirement, you run the risk of letting the “ magic smoke” out of them. I admit that I have done this in the past. It might not happen, or it happens when least convenient.
Plan for everything you want to add in the future, like electric seats with heaters, electric windows, or whatever you might see in the future. It may save you from the need to expand. If you don’t use a 60 amp auxiliary terminal, it’s just waiting to be utilized, and it’s like many other things.
Better to have it , and not need it, than to need it and not have it.
 

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Tim - The Northwest 1969 Camaro
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For what it's worth, I didn't plan that far ahead either. All these helpful forum members talking me into things I didn't even know existed (Don, John, you know who you are) and the next thing I know I need an 8 gauge here, a big ground over there and what do you know, it all seemed to work out. I was lucky in that I wasn't trying to tie old into new and had a relatively blank slate but still, there was a bit of hair pulling going on. I also spent a bit of time on Protouring.com, LS1tech and the Chevelle forum just to see what others were doing and more specifically, why were they doing it? I was never really concerned about the whole invisible wire, super clean engine bay but I did want things to make sense and route with purpose (the radiator support is your friend).
 

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1969 Camaro Restomod
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I think that should be ok.

I don’t know about other guys but I bring the large battery cable to a stud in the engine bay. From there to the starter, alternator, fuse block, fans etc. This seems to work well for me and I’ve done it on several cars. I think GM does the same thing on their Camaros with trunk batteries. In fact I buy their battery cables from wrecks on eBay for around $50. A real deal imho.

Don
Don...
Is this typically what you buy on eBay? Or if not, a link to something that could be used. Also, how do you run the wire thru the car? Under the sill or what? Could be a winter project. TIA-Mike
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