Wiring a toggle switch for relay...

stock50LX

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Oct 2, 2001
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I am hooking up a switch so I can turn off my electric fan when I want. My question concerns the switch hook up. The toggle switch has two wires, one connects to the relay, to what do I connect the other? Thanks in advance.
 
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stock50LX said:
I am hooking up a switch so I can turn off my electric fan when I want. My question concerns the switch hook up. The toggle switch has two wires, one connects to the relay, to what do I connect the other? Thanks in advance.
the other wire will hook to whatever the wire on the relay you connect to supplies (12+ source or ground).
this depends on whether the fan controller feeds the relay a ground or 12+ to energize the fan relay. once this is known, see below.

if the trigger for the relay is ground (meaning the other side of the coil is a constant positive source), then run the wire to a good ground.

if the trigger for the relay is positive (meaning the other side of the coil is a constant ground), then run the wire to a 12 volt source (often something that is key on only, so the fan doesnt try to run all night if you forget to turn it off).

if it is a positive source you need, the actual source is not important, if the correct relay wire is tapped. you will only draw a couple hundred mA to energize the relay; the wire from the battery/starter solenoid will actually supply the power to the fan.

make sense. easy concept, hard for me to explain clearly.
 
You can wire the switched side of the relay any way you want, but you DON'T want a 12v switch. You can cause a fire should somethig that is grounded happen to hit it while it is installed in the interior. You want to make it a ground switch, so put ground one end of the switch, and put the other end to the switch side of the relay, and put the other switched side to the positive side of the battery. When you flip your switch, you will complete the ground, therfore switching the relay and turning on the fan.

BTW my friend wired his the wrong way, and sparks were flying when we try to take out the switch. Don't hook up the relay to the battery till you aree done installing everything, then double check your connections.
 
As an electrician by day, i can tell you there is a really easy way to wire up your fan. the first side of your switch will be wired to the fan. Most electric fans have a wire comming out of them that reads "12DC" this is the wire that you will connect to the first side of your switch. Now if you want to be able to turn the fan on all the time(even when the key is not in the "on" position in the car) then connect the 2nd side of your switch to the positive battery terminal, or the positive side of the starter relay. If you would only like to turn your fan on while the car is in the "On" position then the 2nd part of your switch should be connected to the other side of the starter relay. Now if your really lucky and the fan has a wire coming out of it that reads "remote" then all you need to do, is do the same thing that i told you to do with the "12DC" wire, only do it with the wire that reads "remote" and connect the "12DC" wire comming from the fan directly to the positive side of the battery or the positive side on the starter relay. Hope this is alittle easier to understand.
 
POS5.0 said:
As an electrician by day, i can tell you there is a really easy way to wire up your fan.

Seriously...as an electrician you should know that you need a relay (as mentioned in the OP's original message), and that you do not want to just run right off the battery through a little switch.

As for the actual wiring, the first reply was dead on. Just wire it up to somethat that is constant on if you want to be abel to run the fan anytime, or ignision on if only when the car is running.
 
like everything, there are a million ways to do it. the way i outlined is how i would do it - i would utilize the relay already in place for the fan.

Black Fox, i normally agree with you, but our opinions differ here. when running the 12 volt wire to the relay (if that is what is needed), the relay will draw around 120mA (standard Bosch SPDT relay). he can ohm the relay out if the wants to know for sure- moot point.
that is not much power being fed through the firewall, should a short occur. if he needs a 12 volt source, and wants to do it your way, he could use another SPDT relay to convert a ground pulse to a positive pulse, but i dont see the point (just to avoid running a 0.1 amp-drawing wire through the firewall). stick a fuse on the wire from the 12 volt source to the switch (didnt mention that, as i figure most people know to use a fuse on ANYTHING tapped from a larger circuit). a one amp fuse is enough.
let me ask, did you convert your car so that you have no positive flowing wires going through the firewall? if i read your post correctly, that is what i would think you did, since it is dangerous, per you.

i would never run a fan with a switch handling all the power. that is a possible fire waiting to happen. not to mention running 20 amps (or however many amps is needed for the fan) through a great length of wires, through the firewall (twice). a relay under the hood would keep all the high amperage juice in the same proximity and is much safer, IMHO.

i apologize if i angered anyone, that was not my intention. i am in a marginally bad mood and dont like to see (what are to me) unsafe or illogical suggestions made. we are all cool with each other and this is my two cents worth. 89 GX, thanks for the props. i think it makes sense (it would be easier to lay it out for him if we knew if the controller sent 12 volts or ground to the relay to activate the fan). i have seen and worked with both.
 
I have only the ground of the switch side in my interior, the SWITCHED side (the side that handles the high current is grounded in the engine bay)

I didn't really understand what you were asking me. I have no problems, nor have I had any problems running my electric fan for over a year now, When I race during the summer, I use the switch to cool my car before runs, I would leave the fan on for a while at a time, no problems.....when I use the A/C it is on with the compressor. maybe you miss interpreted my post, or I just put it the wrong way or with insufficent detail. If thats the case, then my apologies....
 

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BlackFox5.0 said:
I have only the ground of the switch side in my interior, the SWITCHED side (the side that handles the high current is grounded in the engine bay)

I didn't really understand what you were asking me. I have no problems, nor have I had any problems running my electric fan for over a year now, When I race during the summer, I use the switch to cool my car before runs, I would leave the fan on for a while at a time, no problems.....when I use the A/C it is on with the compressor. maybe you miss interpreted my post, or I just put it the wrong way or with insufficent detail. If thats the case, then my apologies....
Black fox, i must be missing the boat on what you are saying.
what i thought you meant was: let's say he needs to send 12 volts to the relay to energize the relay and fan (meaning that the controller sends 12 volts to the relay to turn on the fan-some do, but is not common). then he would need to run the ground switch you suggest, but then use another relay to convert the ground to 12 volts. i saw this as unnecessary.

and now i see what you were saying, i think. assuming he needs a ground pulse to energize the relay (i tend to use whatever the controller sends from the probe - often ground), then your idea is great.
i would still run the ground wire to the relay's ground coil input (i.e, terminal 85), and use the relay to power the fan.

im confused now, but i think that is what you did, and that is how i would do it. i was trying to explain it both ways, in case he needs to run a positive pulse to activate the relay and fan. i thought you said to never run a 12 volt wire through the firewall, as it risks a fire. the only time i see that as a possible risk (assuming fuses and correct AWG wire is used), is doing a switch with no relay, as was suggested by someone else.

as i said, we are cool. i think i mis-understood what you meant. in wiring especially, it's hard to articulate, but a simple pic makes it all clear.
:cheers: Black Fox
 
Well this is the diagram I used....(you might have to copy and paste it into your browser)
http://www.geocities.com/smithmonte/Auto/FanControl.jpg

See how the magnet side of the relay has a switched ground? thats what i meant, and have in my car, no need for an extra relay, the other relay is for a positive switched electromagnet.... follow me now?

This is just one big mess, relays are always confusing, lol i hope this clears it up :)
 
IndyBlk5.0 said:
i want to do a 3 way toggle switch, i am going to be running a 70-75 amp relay... my fan is a dual speed, how do i wire this three way toggle switch to it?

I'm assuming this is an ON-OFF-ON toggle switch and you want HI-OFF-LOW. If that's the case, I think I would set it up as two different relays, but use the same locations, power sources, etc. for each terminal on the fan (HI/LOW). Then when it comes to switching the relays, that's where you use your one switch. One side will energize the LOW side and turn the fan on low, one will turn the HIGH speed on with the other relay, and the center will be off.
 
Stock LX, glad to hear you are done, but we are not done beating this to death. LOL

Black Fox, every time i try to load something from Smithmonte lately, it wont load. i know what you mean though, i think. your fan controller must send a ground pulse to the relay, right? if so, then everything you said makes perfect sense.

i was trying to cover both possible situations (it uses a ground pulse or a positive pulse). now you will see this point. if he needed a 12 volt pulse instead of ground, but wanted to use your method of running ground through the switch, he would need to run the ground wire from the switch to a relay to convert it to 12 volt output, and then run it to the fan relay. that was where the second relay came in. cool? that is what i was talking about (or trying to).

i guess it is universally known that fans in stang applications use a ground pulse (i did not know that). one of the italian cars i have uses 12 volts, as do some other italian and "imperial" cars. had i known for sure that he needed a ground pulse, we could have saved some typing. in lookin at it, that is what i said (it reads that way to me atleast. LOL) and what you said. i just confused everyone with the whole "if it is 12 volt triggered" stuff. we be cool! :)