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Where To Find 12v Ignition Wire In Engine Bay

Rekin

By Rekin,
in Car Audio & Electrical

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Rekin Grand Master

Rekin

Posted
Posted

Hello all,

I need a 12v ignition wire to turn on my thermo-fan controller in the engine bay.

Can someone please point out where I can get a 12v ignition signal from? Somewhere on/near the relay/fuse box?

I also need a 12v Aircon signal wire in the engine bay (would prefer to have it somewhere close to the battery and not the actual wires near the compressor)

I have read that the relays in the fuse box are negative switching (ie. constant 12v and activate by grounding)

Any help would be greatly appreciated!!

Thanks

Rekin Grand Master

Rekin

Posted
  • Author
Posted

The lot of you are useless!

Turns out there is a constant 12v going through the fuse in the engine bay. Couldnt find a 12v ignition so had to wire into the drivers side and piggy back off one of the fuses near the foot well.

Hopefully someone will know the answer to this question;

I need a 12v ignition source which ISNT accessories. ie. Once the engine is started and running then I have 12v. Not during Accessories.

Im thinking the 12v source for the injectors? Or is that on during accessories?

Thanks

jrm Veteran

jrm

Posted
Posted

Put in a relay... run the signal wire to something inside the car if necessary for an ignition signal - and use it to switch the supply from the battery. Simple & clean. Hell, do it nice and tidy and put the relay inside the fuse box in the engine bay like the others to make it nice and factory-looking.

Rekin Grand Master

Rekin

Posted
  • Author
Posted
Put in a relay... run the signal wire to something inside the car if necessary for an ignition signal - and use it to switch the supply from the battery. Simple & clean. Hell, do it nice and tidy and put the relay inside the fuse box in the engine bay like the others to make it nice and factory-looking.

mm, prob is I dont know what unit requires 12v after engine start haha. Everything is usually powered when key switched to accessories. ie. fuel pump prime. Only thing i can think of is injector voltage, but not sure if thats provided power during accessories or once engine is cranked.

  • 2 weeks later...
blk94r33 Mentor

blk94r33

Posted
Posted
mm, prob is I dont know what unit requires 12v after engine start haha. Everything is usually powered when key switched to accessories. ie. fuel pump prime. Only thing i can think of is injector voltage, but not sure if thats provided power during accessories or once engine is cranked.

Alternator? I think. There should be something that you can tap into that only powers up once the car is running, to prevent the alternator from trying to charge while the starter motors doing it's thing. Don't mean to be vague but not %100. Or buy a cheap shift light and set it to 800 rpm with a relay running off t?

Rekin Grand Master

Rekin

Posted
  • Author
Posted
Alternator? I think. There should be something that you can tap into that only powers up once the car is running, to prevent the alternator from trying to charge while the starter motors doing it's thing. Don't mean to be vague but not %100. Or buy a cheap shift light and set it to 800 rpm with a relay running off t?

ah alternator that sounds like a good idea! Might trace back the wiring from the alternator and see if there is any easy place to splice into.

Thanks for that.

blk94r33 Mentor

blk94r33

Posted
Posted
ah alternator that sounds like a good idea! Might trace back the wiring from the alternator and see if there is any easy place to splice into.

Thanks for that.

No worries, not trying to be a smart ass or assume anything, but I meant one of the thinner wires coming out of the reg, not your main battery wire as this will have battery voltage all the time. The wire that switches the alternator light on the dash is the one I'm thinking of.

3LGODZILA Proficient

3LGODZILA

Posted
Posted

tap into the main harness comming off the key switch then run it outside its not that hard, i wouldnt even think about splicing off the injectors!

if ur set on getting an ignition off ur alternator then ill tell u what to do, i dont recommend it but, most will have a main battery (obvious) and a plug with 2 or so wires, 1 will be warning light (dont splice into this) and the other will be an ignition feed. the warning light will have a negative there when the keys on (which light up the warning light on ur dash) then once its charging it turns into a positive which make 2 positives going to the gobe on the dash (which cancels out the light)

and this is how to wire it up to a relay - please dont just run them straight off the ignition feed otherwise u'll blow fuses left right n centre.

85 - ignition source (in ur case spliced off the alternator)

86- earth

87- to ur thermo positive wire(s)

30- straight to the battery (use an inline fuse @ the battery) a standard 30amp relay will be fine

this way when u turn ur key on to ignition the relay will energize sending power straight from the battery to the fans, turn the key off fans go off, this is how u wanted it wired up right?

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