How do I create a NEW 12V ignition circuit?

CaifanSC

SCCoA Member
I want to hook up my IC fan but I dont want to splice a 12v ignition wire (radio, lamps, etc) that already exists. I would feel much better somehow creating a new dedicated circuit for this purpose. Any suggestions?
 
I would use a relay. They are cheap and easy to install. I bought one at Circuit City for 6 dollars.
 
OH, that I must clarify. I am using a relay for the fan, but (and please correct me if IM wrong) im under the impression that you need a constant 12v (that im getting from the battery and which will turn on the fan) and you need another 12V to close the contacts for the relay...and this one I want to be ignition controlled. Just so that if I turn the car off and the fan i still on, it will shut off with the key. Again, i really dont want to tap into an existing ignition 12v to close those contacts, but i also dont know how to create a new circuit. Help? hehehe :D
 
a few ways to look at it ..relay would be the way to go ...power from Bat. to relay ..to fan ...on the otherside of the relay ..go from run position of ignition switch...to switch.. to relay...[only needs power when it is running]..and you don't have to turn it off ..by hand ...so won't forget about it ...and drain the battery...then again you could use a themoswitch.. to turn the fan on and off ...without a hand switch...and wire a light LED into the curcuit to show it working ..some good reading on relays and wiring here ...http://www.the12volt.com/ ....dave
 
Rich at mn12performance.com wrote a how-to article on this. In it, he splices the "power" line needed for the fan into something called the "175amp Megafuse" in the power distribution box. The relay activation lead is a low draw lead and can be powered (activated) by just about any run time lead.
Fred
 
CaifanSC said:
OH, that I must clarify. I am using a relay for the fan, but (and please correct me if IM wrong) im under the impression that you need a constant 12v (that im getting from the battery and which will turn on the fan) and you need another 12V to close the contacts for the relay...and this one I want to be ignition controlled. Just so that if I turn the car off and the fan i still on, it will shut off with the key. Again, i really dont want to tap into an existing ignition 12v to close those contacts, but i also dont know how to create a new circuit. Help? hehehe :D

You have a number of options for creating a new circuit for closing the relay contacts:

1) Connect to an unused terminal on the ignition switch. Terminal A1 has power in RUN and ACC.

2) Insert a tap at one of the fuses in the dash fuse box. I would not recommend using the type that is inserted along with the blade of the fuse as this will damage the female pin in the fuse box. There should be other types of taps that don't cause damage.

3)There are numerous male to female connectors in the car that have one wire with power in RUN. Select a suitable pair, then get a set of spare male and female connectors from the junkyard along with a few inches of wire, and then insert the new connectors in between the existing ones. Connect the appropriate wires to each other between the new connectors and add a splice for your fan relay.

That's all that I could think of.

I hope you've fused the 12v wire from the battery.
 
Thanx for the responses guys...they're all great. About that the12volt website....its awesome, its got some interesting projects with relays that i might do at a later time (in particular the radio on until door is opened thing). Thats also where i went for reference when working on turning the Trac Assist button on the automatic 94-95 sc's to power the pusher fan for my 94.

Oh,and JD...that 12v from the battery will undoubtedly get fused.
 
CaifanSC said:
Thanx for the responses guys...they're all great. About that the12volt website....its awesome, its got some interesting projects with relays that i might do at a later time (in particular the radio on until door is opened thing). Thats also where i went for reference when working on turning the Trac Assist button on the automatic 94-95 sc's to power the pusher fan for my 94.

Oh,and JD...that 12v from the battery will undoubtedly get fused.


Here is a link from MN12 Performance that tells you where to tap in for 12 volts (ignition on only) to activate the relay.

http://www.mn12performance.com/mn12how-to/fan-kit/fan-kit-94-95sc.htm

David
 
That looks like clean install. The only thing is that in my case, i wont have the fan turn on every time the ignition is on...i have it wired up to a switch in a custom switchpanel i put where the ashtray used to be. I was thinking of tapping the cigar lighter circuit, but thats hot all the time...so tapping the A1 spot of the ignition switch, which is on in Run and Acc., sounds really good now.

The one thing i do like about the mn12performance set up is the sleek relay they used. I wonder where he gets them from. Im just using a regular 30A bosch relay and pigtail socket. Also, i had not thought about getting constant 12V from the megafuse instead of straight from the battery. That will look much cleaner also.
 
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That looks like clean install. The only thing is that in my case, i wont have the fan turn on every time the ignition is on...i have it wired up to a switch in a custom switchpanel i put where the ashtray used to be.

You can still get power from the same place and just run the wire to your switch panel or use the hot side of the fog lamp swith. BTW, Instead of attaching directly to the battery for power, it's much easier/cleaner to get power from the hot side of the starter relay.

David
 
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Ok, one quick question.....if I get constant 12 V from the ignition coil or the mega'FUSE'...would i still need to put a fuse? I came a bit confused b/c if I connect it to the 'megafuse' i get the impression that this thing should already be 'fused'. In the write up from mn12performance I dont see any fuse. What do u guys think?
 
CaifanSC said:
Ok, one quick question.....if I get constant 12 V from the ignition coil or the mega'FUSE'...would i still need to put a fuse? I came a bit confused b/c if I connect it to the 'megafuse' i get the impression that this thing should already be 'fused'. In the write up from mn12performance I dont see any fuse. What do u guys think?

Yes, you will still need a fuse sized for the device and relay you are using. If it's an IC fan 20 amps should be plenty. The MN12 harness had a fuse pre-wired into it.

David
 
Ok, great to know...i was planning on putting a 30A minifuse inline...should i put a 20A, or will the 30A be ok?
 
Do you know the wattage or amperage of the fan? You can find them on the fan motor label.
As David said, the fuse should be sized for the device and relay you are using. And don't forget the gauge of the wiring.
 
The fan apparently says nothing, but i found it on the box. Its an 8" Perma-Cool fan:

motor rpm: 3400
Amp Draw: 4.5
CFM: 800
Fuse size: 15 amp min.......what does this mean, that i can use anything above 15 amp?
 
It means that the fan motor draws enough AMPs at start up to blow a fuse smaller than 15 amps. I suggested 20 amps because it is large enough to handle the amperage draw but small enough that it will blow before melting the wiring on your fan or damaging the relay if something goes wrong. Going with too large of a fuse defeats the purpose of having one.

Things always go wrong with my car...better safe than sorry.

David
 
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