wiring fans up with switches, have a question?

[blacksheep]

click

I have these switches I will be wiring both fans to?

I am going to use add-a-circuit fuses to tap off the fusebox and run them to each fan switch...This way its fused and ready to go. I am running a 20A fuse to each.

So, why does one of them need to be connected to 12V constant? Wouldnt that make them run all the time?

Can I tap into 12V acc fuse and send it to the middle prong since I want these switches to work only when key is in acc position.

I doubt I want them running all the time and drain my mini battery, right? Thats my thought atleast...

Thanks!

 

[Polish]

Correct, that is fine. Unless you want to be able to turn the fans on with the car off like a lot of folks. /ubbthreads/images/graemlins/idea.gif

 

[jepherz]

Yes, and running them when the car is off wouldn't do that much anyways since the water won't be circulating.

 

[blacksheep]

I will forget, walk away, start gabbing and kill my battery in a jiffy....If I had to, I'd just leave key in acc and run fans like when I am waiting in line in auto-x etc...

 

[jepherz]

You are using relays in the mix too, right?

 

[blacksheep]

what relays? No, nothing like that. why?

 

[blacksheep]

the instructions with fans said nothing about relay, Jeff. Those things are confusing and have like 10 poles on them and I dunno wtf to do with them /ubbthreads/images/graemlins/frown.gif

 

[jepherz]

Seems like it would be a better ideal to me, but from their info the switches can handle 10A at 250V. Not really sure what this equates to at 14V, maybe way higher? Then you can get away with running smaller wiring in the cabin and just use the factory wiring in the engine bay to actually power the fans.

A standard bosch relay only has 5 poles, 4 of which you'd use and they are pretty easily explained.

 

[Rausch]

Easy to wire up, and unless the switch can handle the current, you'll need them.....

 

[vtecds1]

Thats the same exact one that I have wired to my fan and the same exact wiring diagram. Works for me...

 

[number3]

 

[blacksheep]

Quoting vtecds1:
Thats the same exact one that I have wired to my fan and the same exact wiring diagram. Works for me...



Confused - Which one, Mine or Aaron's post?

Jeff - I am using 22 gauge wiring? Is that too thin?

Aaron - So from my accessory source, I send +ve to acc prong on switch and then negative to pole on the relay? Confused...

 

[Rausch]

85 - Ground (chassis)
86 - Your switch. (pull power from an ACC location. power from acc into switch then out of other pole on switch to relay)
87 - To fan(s)- Other side of fans gets grounded
30 - Fused power from wherever (You can pull power from the Batt, and install an appropriate inline fuse.)

That's it man!

 

[jepherz]

Quoting blacksheep:
Quoting vtecds1:
Thats the same exact one that I have wired to my fan and the same exact wiring diagram. Works for me...



Confused - Which one, Mine or Aaron's post?

Jeff - I am using 22 gauge wiring? Is that too thin?

Aaron - So from my accessory source, I send +ve to acc prong on switch and then negative to pole on the relay? Confused...



22 gauge for powering the fans? or just for running from the switch to a relay? In either case, I'd say that's way too thin. I'd want to go with 18 probably for the switch, and maybe 12 for the fan power?

Another advantage of using relays (may not work in your case since your switch has an LED in it) is that you can just run the ground side to the switch and ground the other terminal right by the switch. This is how you'd probably go about putting a fuel pump cut off switch.

Don't let those diagrams confuse either. You can actually wire it up backwards and it's the same thing.

 

[Rausch]

Whoop, just loked at your switches..... They would connect the same, save you'd need to ground the one that is marked ground as well to get the LED to work.

I'd also suggest heavier wire for the wire from teh batt to the relay, and the relay to the fans. 12ga would be fine.

You can go thinner on the switch wiring, as it's not carring much current, but 22 is pretty darn thin....I almost always use 16ga when wiring up switches.

PM or give me a shout if you need any more help . /ubbthreads/images/graemlins/grin.gif

 

[BoostedAWD91]

what kind of relay are u guys using? probably any relay would work for the most part i would think. i have my one fan wired to a switch right now and i got a high amperage switch and it has worked perfectly without a relay but i figured i should ad one in the circuit just to b safe

 

[toybreaker]

There should be an anti fly back diode installed in the circuit to protect the relay (or switch) contacts.

> edit
Fan motors are an inductive load, and the switch in that link is for a lighting circuit.

When the current stops flowing in a motor, there will be a spike of current flowing in the opposite direction a mili-second after the points open. This is due to the magnetic field collapsing in the motor windings, and it will produce a jigawatt of current which will flow backwards in the circuit and arc across the points, eventually burning them, and rendering the switch (or relay) contacts in-operative.

 

[Rausch]

Bosch style relay is what is essentially in the pics above. You can usually grab them at the auto parts store for fairly cheap. They will sometimes have generic wiring kits as well, but if you're wired up/and have some extra wire, just grab a relay.


As a point of reference, the 87a terminal on teh Bosch style relay could be used when your switch is meant to 'switch' power between two different components. In one switch position, the relay would supply the 12v power to whatever is connected to the 87 terminal, and in teh other position, it would supply power to the 87a terminal. If you are just trying to get power to one component, just use the 87 terminal.

 

[jepherz]

Quoting toybreaker:
There should be an anti fly back diode installed in the circuit to protect the relay (or switch) contacts.



John, this is true, although is it that necessary for a switch? I've never used them on switch activated relays, as I figured that's why they made relays without the diode. I'd always use them when activating the the relay with a FET or something similar; I've had some circuits burn out from this /ubbthreads/images/graemlins/banghead.gif

 

[toybreaker]

Jeff, it is only the switching contacts that need to be protected.

If the switch is switching a relay the switch should be fine, and the relay should be protected.

If it's just a switch doing the work, the switch will need to be protected.