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Discussion Starter · #1 ·
I have Deralle twin fans and was using there fan controllers until I got them wet, don't get them wet.%^$*$&@^#&$
I am replacing them with a Spal unit, the Spal directions show the main power leads going direct to the battery.
I have my car wired for 3 wire internal reg. Alt with voltage sensing.
If I hook the fans/controller direct to the batt. will it mess up my charging system?
Or should I wire into an aux. fuse block I have up by the horn relay that gets it's power from the Alt.?
Any opinions or advise is welcome
T.C.
 

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i would hook up the fan power to relays, and have the controller switch the relays on/off. You can run power direct from the battery, just make sure its fused and you have a large enough size wire.
 

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yes, the power leads go directly to the battery.
of course, there should be relays with temp switches involved in there somewhere, as well.
i just took the entire cooling fan and harness with relay and temp sender directly out of an 86 Chev Celebrity to keep my Monte cool. it hooks right up to the back of the alternator, but i'm going to move it over to the other side to hook it up to the battery come spring when i put the 94 Caprice radiator and dual cooling fans in.
i found a temp switch at NAPA for $30 that fits my application.
 

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"Or should I wire into an aux. fuse block I have up by the horn relay that gets it's power from the Alt.?

In your case it would be better to connect the fan supply to the horn relay. I would use an auto fuse/self resetting circuit breaker rather than a fuse. As stated above, use relays.
 

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Discussion Starter · #5 ·
Thanks for the replies
Either way the fans will be going through relay's using at least 10 gauge wire and a temp sensor.
I guess my real question is where to hook up to not how to hook up. (except for the resetting fuse, good idea)
So I have two people who say go direct to battery, and one to aux. fuse block?
I was thinking if I go directly to the batt. the Alt. wouldn't sense the draw of the fans correctly and not put out the correct amount of voltage ?
According to the MADD wireing diagram they should go to the horn relay. In my case I have replaced the horn relay buss bar with a fused junction block so I can hook my headlights, vacuum pump and fans? to it.
T.C.
 

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Very basic, and often misunderstood, and I will say it again: electrical system power/current does NOT flow from the battery when the engine is running. It comes from the alternator.

If you go direct to the battery you are increasing the wire run to power the fans and putting another connection into the adverse environment of the battery. Neither of these are good things.

You are also limiting your fan supply to the 10g wire that runs from horn relay to battery. This may be a factor or not...

Sounds like you already have a fuse block and supply next to the horn relay, so connecting your fans anywhere else would be second best.
 

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Discussion Starter · #7 ·
Thanks again for the replies:
That's what I thought, but the directions and the tech. at Spal said to hook up directly to the battery.
Actually I have a fused buss bar that is taking place of the horn relay, it is getting it's power from a junction block at the fire wall via 10 gauge wire.
The junction block on the fire wall is getting it's power from the Alt. wire that is routed through the starter, using 8 gauge wire.
Do you think the 8 and 10 gauge wire I have going from alt. to starter to the fused bus bar is to small for the fans I have?
(Deralle 4000 cfm)
T.C.
 

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So if I understand correctly...

The alternator power cable runs down to the starter. Then another cable runs from there up to the junction block on the core support behind the battery?

And from there it is basically stock with the original 10g wire running across the core support to the bus bar on the DS?

And the sense wire bypass all of this and just runs from the alternator to the bus bar? Does it go around the cape to get there too? ;)

I am not surprised a tech would tell you to hook it to the battery. This is a lowest common denominator solution and they are not intimately familiar with every car design out there. Does not make it the best though.

Regarding wire size though, you have to consider the current draw of the entire car at it's worst case (cooling fans, HEI, A/C compressor, heater fan, wipers, high beams, stereo blasting :thumbsup: ). That is what your alternator has to feed. Compound that with a significant length of wire run. Add in some high temperature around the exhaust. This setup will run everything through that 10g up front and that may be the weak link. That can cut the safety margin a little small for higher current flows. It is probably capable and it will probably work but it does not give me warm fuzzies either.

You are kinda stuck with the PS alternator setup... but a better setup IMHO would be to run a new alternator power cable on the order of 6g back to the firewall, across the top, and down the DS fender to the bus bar (this might be how your sense wire runs?). This will offload the 10g across the front and allow it function as a battery charge current limiter again. You will want a serious fuse at the bus bar on the alt power cable, something like 125A minimum. Because if this cable ever shorts it will be entertaining. American Autowire sells a couple mega fuse assemblies that would do the trick.

Here is a table relating current and length for power cables:
http://www.powermastermotorsports.com/charge_wires.html
 

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Discussion Starter · #9 ·
No, no, ya got it all wrong, or maybe I do?
Please let me try to explain:
The Alt power goes to the starter, from the starter it goes to a junction block on the "firewall" beside where the main wire harness plugs into the back side of the fuse block "Under the brake booster".
From there it goes to a fused buss bar that I have mounted inside the front drivers fender well.
This fused buss bar is taking place of the horn relay buss bar, I have nothing going from this buss bar to the battery, and the only thing I have wired direct to the battery is the MSD box.
I am running the head lites w/relays, the fans w/ relays and a vacuum pump w/relay off this fused buss bar.
I have the voltage sensing wire from the alt. going to the junction block at the "fire wall" this is also where I have the main power lead for the rest of the car hooked to.
I tried to wire the car like the MADD directions that everyone said is the way to go?
So this fan controller directions say to wire directly to the battery ?
Thats where I am getting confused?
Also just so you know, I dont have helter skelter patched up wireing, my wires are "very" neet and everything is krimped,soldered, shrink wraped and then wraped with friction tape.
So were no dealing with some jumbled up mess here, not that youall said or implied that, I just wanted ya to know.
This is what I have.....................hopefully, see picture?
 

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Oh. The picture helps. One clarification: does your alternator go direct to the junction block as shown in the picture? That would be better than running to starter and then to junction block.

In many ways this is similiar to what I was suggesting. In fact the more I look at it and think about it, the major difference is that you have the junction block on the firewall while I was thinking about this junction up front on the DS core support. Note I also confused things by thinking about how the factory often used a junction block up behind the battery.

The fundamental idea of hooking up to the forward "bus bar" still works and is still much better than the battery. The comment about allowing the 10g wire to serve solely as the battery charge wire also still holds.

The way I put together my system was to use a power distribution box from a Ford Taurus up on the DS core support. This box provides the 175A mega fuse to protect the alternator power cable, the junction block, a bunch of 30A+ maxi fuse sockets, 3 regular Bosch relay sockets, 3 micro Bosch relay sockets, and a few regular ATM fuse sockets all in one nice tidy box with a lid. I made a bracket to attach it and it looks like it belongs there. From the box I have the 10g wire going across the core support to the factory junction block and the battery. I also feed the dash fuse block off a 60A maxi fuse.
 

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Discussion Starter · #11 ·
The wire coming from the Alt is going to the starter, I wired it that way because I was going by the OE wire diagram at the time.
I have sense tried to wire it according to the MADD diagram and either didn't feel it made much difference or just missed it?
Anyway plans are to change it eventually, and from what you are saying I should use #6 wire?
That's going to be funny looking hanging off the back of the alt, isn't it?
Here again I may be wrong but I seem to remember reading on then MADD website not to use the giant wires ?
They said it wasn't needed and it would make the sensing system not as effective.
As I said I could be wrong or misread the article?
I am not an electrical wizz, I can solder very well and I understand the basics, but I get in over my head sometimes.
The only problem I was having with my system as I had it wired, (other than junk fan controls) was the lites would dim and the motor would loose about 300 RPM when both fans came on .
I am hoping the new fan control will solve that problem as they say it will turn one fan on at 1/2 speed until the motor reaches a certain temp, then it will turn the other on full.
When the motor reaches the preset low temp again it will turn the 2nd fan off and cut the 1st fan down in rpm until more fan speed is needed, according to the temp of the motor.
This should take some load off the charging system?
I hope?
I think I will take your advice and hook the fan controller to my buss bar at the fender well, then reroute my wire from the alt direct to the junction block at the fire wall.
Then see how it works, I would think this would be a common problem and there would be a simple fix? Guess not.
Thanks T.C.
 

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Part of the problem here is that the electric fans can pull serious current. I have a basic dual fan Taurus setup and at startup they pull 70+ amps. Once running that drops to 15A. Needless to say there is a bit of a jolt to the electric system then they turn on in the full high speed mode.

Ford was a bit creative in how they wired up these fans. They were computer controlled and the schematics use labels like low speed and high speed. The difference was that low speed included a big old ceramic high power resistor in the circuit. I finally figured out that the resistor was not so much to reduce speed as it was to cut the startup current by 50%. A 35A startup current causes much less system burp.

A 100+ A alternator is a fairly modern part and it is very common practice to have rather large wires on the power feed. For these large currents you need a much larger pipe than the old 35A models our cars came with. Yeah the 6g cable is perhaps on the large side, but then you have a fair distance the cable is running to compensate for as well. And within reason tis better to have too much than too little.

Put another way voltage drops because of resistance to current flow. If you put 15v into one end of the wire but only get 14v out the other end you have lost some energy, electrical in this case. That energy goes somewhere and in this case it goes into heating the wire. We have all seen 1500 watt resistive heaters... well calculating the watts of heating involves resistance X current X current. So if you are pulling a 50A load... that is 2500 X wire resistance, or 0.6 ohms resistance to provide heat equivalent to that 1500 watt heater. You really do not want much resistance here at all. If you want to delve into it you can find resistance ratings for wires on the internet and compare.

I would do some investigation into your fans and what their current draw is during operation. Likewise at startup. You can calculate the latter by measuring their resistance with an ohmmeter, then divide 14 by the resistance and you have current. My fans for example measure 0.2 ohms, which is how I figured the 70A startup surge current (and the "low speed" resistor is a similiar 0.2 ohms giving the 50% reduction). Note that effective running resistance is much greater due to magnetic inductance (the motors also work as generators). While running my fans provide 0.93 ohms (14v divided by 15A).

So long as you run through relays you are going to be a bit limited in what you can do about fan load. About all you can do is start the fans one at a time, if the controller is capable. With a more advanced (and more expensive) high power fan controller designed to not use relays, you can implement soft start current limiting. You still cannot reduce the current of full speed operation though.
 

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Discussion Starter · #13 ·
Thanks for the reply:
I appreciate all your time explaining this to me.
I think the controller is soft start for the #1 fan as it uses no relay, however it uses a relay to switch on the second fan.
Probably should buy two controllers $$$$$$
So if I replace my alt wire with 6 gauge wire and put a 150Amp resetable fuse at the fused buss bar, and wire it like the drawing then I should be good to go, rite?
I assume the 10guage from the firewall junction block to the starter post will be good for charging the battery.
T.C.
 

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The way I put together my system was to use a power distribution box from a Ford Taurus up on the DS core support. This box provides the 175A mega fuse to protect the alternator power cable, the junction block, a bunch of 30A+ maxi fuse sockets, 3 regular Bosch relay sockets, 3 micro Bosch relay sockets, and a few regular ATM fuse sockets all in one nice tidy box with a lid. I made a bracket to attach it and it looks like it belongs there. From the box I have the 10g wire going across the core support to the factory junction block and the battery. I also feed the dash fuse block off a 60A maxi fuse.
Man, I'd love to see pictures and a diagram of that setup. Pete
 

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Discussion Starter · #16 ·
Thanks again for all the help:
Would I put the 150A breaker close to the alt. or close to the fused buss bar at the DS front fender well?
If by the buss then what protects it from the alt to the buss?
Or am I wrong once again?
Thanks T.C.
 

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That is a pretty good question and one I pondered quite a bit trying to figure out what Ford on the box I have. The 175A mega fuse was not hooked up as I had expected at all:

battery-------x-FUSE-x-----------------------------Alternator
. . . . . . . . . . |
. . . . . . . . . . |
. . . . . . . . bus bar

(ignore the dots... silly BBS eats leading spaces :mad: )

In effect the mega fuse is not there as a master fuse at all (as I had initially thought). Instead it is there to protect the alternator power cable from battery powered shorts.

So the answer is you put the 150A breaker close to the fused bus bar or at the end of the alternator power cable furthest end away from the alternator.
 

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Discussion Starter · #18 ·
So the alt wire doesn't need protecting, or should there be a fusible link?
It's not now so I guess it doesn't matter?

T.C.
 

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You are protecting the alternator power cable via the 14g fusible link you show next to the battery. So you don't really need that 150A fuse by the bus bar.

In the Ford application my power distribution box comes from the battery is right next to the box. So there was very very little exposure of a short between battery and fuses. Of course the Chevelle is setup a bit differently... so one of my future plans is to replace the junction block on the PS of the core support with a mega fuse block I picked up some time ago. This will remove my current exposure on the 10g wire running across the core support. Yeah it is probably not much exposure which is why it has not made it to the top of the project priority list yet :)
 

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Discussion Starter · #20 ·
Re: Fan wireing opinions please "update"

Just wanted to let you guys know the system is working fine and to thank you for your input.
I replaced my punky alt. wire with 6 gauge and installed a Spal fan control.
The control works really well and doesn't seem to have as much "start up" draw on the system as the Deralle units had.

If I may get another opinion?
Would I be better of with my "sensor" wire going to the aux. fused buss bar at the front of the car, or leave it at the fire wall junction block more in the center of the car?
Thanks T.C.
 
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