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Rooinater

"How To" wire dual fans with on/off/automatic toggle switch

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well... i wrote up and drew a diagram. So that you can wire your cooling fans for a 3 position switch. giving you the option of

 

-ON-

for those trails and days your engine just needs a little more cooling air to be sucked through. or those hard days on the trails in the hot weather.

 

-OFF-

for water crossings and deep water forgings. to help eliminate the possibility of breaking a fan blade and putting it through the radiator. also to help keep the splash down on the engine or near the intake.

 

-AUTO-

for your day to day usage.

 

the really great part of how this diagram has you wire it is. you never will have a dead battery cause you left the fan in the on position. by running it off of the coil to activate the relays. it causes it not to be able to work unless the key is in the start or on position.

 

hope you enjoy or this helps you out. let me know what you think.

http://www.westcoaststompers.com

go to subaru modifications, then to the fan modification. too lazy to link it

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Roo In, nice setup. here is one a little less

intense.

If you want the "off feature"

Run the tank switch contact that now goes to the relay to the other pole of an "on-off-on" type switch.

fanwire.jpg

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Jared I have duel fans but only with the on/off toggle this i will probobly do for like you say, day-to-day driving :cool:

-Sean

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the diagram i drew is actually really simple. i used 2 30 amp relays for the reason of not really killing relays. all the wires are tied into a wire bundle across the lower portion of the fans.alongside the battery. the relays are next to all the other relays by the battery. and the rest of the wires are tucked along the firewall with the window washer lines. under the fuel pump and into thecab via the little wiring grommet on the drivers side. very clean. and you can route them almost invisible if you wanted to.

 

yes the way you have yours sean is perfectly fine for how and where you use it. my car always had a problem of getting very hot. so i need them on all the time from time to time. extra cooling in warm weather. i'll find where i have that diagram. and i'll put it on there too.

 

if i may i'll add that diagram to my web page if you don't mind. tell me if you do and i'll remove it. thanks.

 

good luck!

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I would recommend sticking with ground-side switching, since that is how the stock wiring is set up. This prevents voltage spikes and such, and is easier on the motors.

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both the diagrams are ground switched. the switches are not on the power side they are on the ground side. so i don't know what you mean. please clarify. cause both those diagrams are considered ground switched.

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Unless I misunderstood your diagram, which is possible because I'm not perfect at reading diagrams yet....

 

Your relays are ground side switched, but they control the power to the fans since they are on the "upstream" side of the motors. Hence, not ground side switching.

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it won't make that much of a differance with voltage spikes. either way you are going to ensue voltage spikes. cause either way you put that you are going to be having all the voltage hit the fans. by wiring all relays to the grounds. you are actually complicating the actual wiring itself. due to having to run more wires. these are electric motors not sensative little electronics. almost all of the components in the aircrafts i work on are switched or relayed before a load. and you are talking about thousands and thousands of dollar computers. i think if there is such a problem with it the whole entire aircraft would not be wired that way.

 

either way you are throwing all the voltage at the fans. the only differance is the voltage on the relay. but no matter what the amperage on the relay will be the same. beings the fact relays are rated at amps for a reason. cause that's the main reason they break down, open or short across.

 

a little note on how electricity works.

voltage is eaten up by the resistance. it should be to approximately 0 by the time it reaches ground at the end of a circuit. amps stay the same in a circuit all the way to the ground. amps create heat which heat kills electronics. hence why we use relays. if we didn't use relays you'd fry those little toggle switches to kingdom come. cause the heat from the amperes will fry them.

 

if you need me to post up the naval and civilian publications of electricity basicis and formulas i will. but i hope i need not.

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strangely enough a small toggle switch has been able to turn my fans on and off for a few weeks now, and it doesnt heat up at all. I agree on the voltage spikes, its all one current flow it doesnt matter whether you are on the "positive" or "negative" side (these are just abstract concepts anyways)

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yes mine worked fine for a few months like that. then it fried out. it takes time. heat unless extreme does not destroy the switches right away. especially if its a high amp switch. it'll slowly break it down. if it's only used from time to time it'll work fine. but as soon as you start using it more often. it's not a good idea. you are asking for an electrical failure.

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Rooinater, I don't doubt your knowledge of electrical and mechanical stuff. Seeing pics of your ride and hearing your stories makes it clear you know your stuff. I was just posting on behalf of what my prof has been telling us in Auto Electrical I and II (currently in III) to try to clarify things a bit.

 

I would agree that it probably doesn't matter to those fan motors, since they are quite beefy electrically, but I usually like to err on the side of reducing as much stress as possible on components. And yes, closing a switch on the power side does send a spike, however small, since the voltage was not previously present at the motor. Closing a switch on the ground side results in no spike since the voltage is already present at the motor. It is my assumption that that is why the factory wiring is set up that way.

 

I also don't see how putting the relays on the ground side complicates the wiring at all. They are merely being connected in a different location.

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you have to run longer wires all over. the actual degree of what you are doing is the same. the way i have the diag. it illiminates all of the stock wiring essentially. cause i don't really trust it. so it's not a cut and splice. the way it's wired right now you utilize a ground off the mountin bolts on the fans. only like 2 inches. otherwise you have to run a wire from there to the relay and to the switches. you can realy wire it any way you want. but this is a perfectly ok system. if you want i'll add that you can put the relays on the ground side of the fan. if i was working with an INS unit or an ADC or something to that complexity i might think about it. but even then if you look at all the wiring schematics for an av8b jet none of them i've seen so far that do not have the switches and relays before.

 

sensors on a car you might want it switched on the ground side. but overall you are not gonna kill the fan easily.

 

one of the main reasons i see that they actually use a ground for the switch. is because that's the easiest way to use a thermalswitch. unless you run power to your radiator and then out of it. using an insulator around the actual thermoswitch. inner conductor being power out and and outer conducter being power in. which would be a lot more complex. the way they have it is one gnd coming in sitting there. and when the semiconductor breaks down it grnds out on the radiator.

 

it's the same design that they use in engine bay fire wire in the aircraft. breaks down gnds out and turns light on. it's just utilizing the thermal switch.

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When the circuit is open there is not ANY voltage at the motor regardless of the switch placement. The electrons sit, present in all the wires and in the motor, and they all begin to move at once in the same direction when the circuit is closed. A positive wire has no voltage or current until it is given a path to ground. It is just labelled hot or positive because that is what it becomes when it finds a path to ground.

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Bushbasher, I would tend to disagree there (well, you already knew that;) ). Here's why though:

 

Say you've got a fan wired with the switch on the ground side. If you were to take your voltmeter and place one lead on the positive side of the motor and the other to chassis ground, it would read battery voltage. Take that same fan and put the switch before it. If you do the same thing with your voltmeter, it will read nothing.

 

There does not have to be current flow for there to be voltage present.

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yes voltage would sit through the fan. if the switch was on the ground side. the side coming from the batt. to the open will have voltage always there. the fan will not turn on till current starts to flow. voltage is a potential and also the motive force that pushes.

 

it's voltage potential that always sits there. it just needs a ground for the circuit to complete and the current to start to flow.

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when you hook a voltmeter there is a path to ground. A voltmeter has a very small current draw. It is not completely passive in a circuit. I'd like to hear exactly how the voltage spike is created.

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What is the purpose of a relay? Can't you just toggle the ground side and run a new power wire with an online fuse?

 

 

The purposes of the Relay are (among others) to let the Thick wiring on the engine bay, to bear with the high voltage / amperage \ heat; while you send only a "signal wire" to the interior. Doing that, will elongate the lifespan of the system, including the Switch itself; also the Fuse lines for the circuit remains on the engine bay, adding safety.

 

Kind Regards.

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