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Thread: Focus 2012 +12V Ignition Help!!! Reply to Thread
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Topic Review (Newest First)
02-03-2017 04:01 PM
MK3 ST3
Quote:
Originally Posted by firebirdude View Post
Once again, maybe I'm just misunderstanding what your point is, as you seem to be jumping down an unnecessary rabbit hole. You stated, "Usually when the radio goes in you can hijack enough of it's wiring to not have to run additional leads." Which doesn't apply to Focus and the need for a +12V switched source of power.

Additionally, we're talking about tapping into an existing fuse block to power an accessory. Not a low amperage on/off signal wire. Be it Focus or not, if you tap into a fuse and run your own wire, you better at least be sure you're not tapping in on the hot side of that fuse, unless you're installing your own fuse as well.

If you want to get your 12V source from elsewhere, sure. But not a single wire in that car is going to like being shorted to ground accidently. That's why a fuse needs to be put in line.
I guess I don't get what your misunderstanding. I'm not trying to be rude here. Sorry if it comes off that way, you seem to know for the most part what you are talking about but I don't think what you are saying is at all correct.

The FCIM (the face plate) has 12V Power and Ground (if MFT is not in the car then it also has Illumination). The ACM has 12V Power, Ground, and "the Start" wire (this makes 12V when the engine cranks). The ACM also has all the stock speaker connectors. The ACM sends speaker signals to the DSP module on Sony branded systems, and the DSP also has 12V Power and Ground connections. The APIM (Sync module) has 12V Power and Ground.

The wires those modules have access to I mean you directly hijack. Otherwise what do you need, Illumination if you don't have the base system, a switched ignition line (Ignition/Run line in Ford speak) and that comes from the BCM, and a reverse signal which you get by tapping into the rear lamp control line.

This to me is pretty standard for audio systems. My Corvette C6 was like this when I installed a system (I had to hijack those 3 signals, I grabbed the switched ignition off the HVAC unit in that car, Illumination of a switch). My GTO was similar only the radio had everything but the reverse signal. Hopefully that cleans up where I'm coming from.
02-03-2017 11:53 AM
firebirdude Once again, maybe I'm just misunderstanding what your point is, as you seem to be jumping down an unnecessary rabbit hole. You stated, "Usually when the radio goes in you can hijack enough of it's wiring to not have to run additional leads." Which doesn't apply to Focus and the need for a +12V switched source of power.

Additionally, we're talking about tapping into an existing fuse block to power an accessory. Not a low amperage on/off signal wire. Be it Focus or not, if you tap into a fuse and run your own wire, you better at least be sure you're not tapping in on the hot side of that fuse, unless you're installing your own fuse as well.

If you want to get your 12V source from elsewhere, sure. But not a single wire in that car is going to like being shorted to ground accidently. That's why a fuse needs to be put in line.
02-03-2017 11:28 AM
MK3 ST3
Quote:
Originally Posted by firebirdude View Post
Maybe I'm misunderstanding you, but they're wiring up an ignition lead to the head unit because there's not one from the factory on the MKIII Focus....and they're too cheap to buy the proper module. lol So I'm not sure what you'd hijack behind the head unit to not run an additional lead?

If the wire you're using the tap in cannot carry the amperage (gauge vs length) of the factory fuse, you need to add your own fuse; be it an add-a-fuse, in-line fuse, etc. Running 16-18awg wire on the factory ignition circuit certainly requires its own fuse.
The ignition/run line comes from the BCM, it's a manufactured signal the wire is always of a thin gage. No need for a fuse. Just find the line in the car (anywhere) and tap into it. Won't cause any harm to any module. The lines level is controlled by the BCM who outputs it. The fuses are to protect only from accidental shorts, nothing else.

A higher amp would just lower the voltage because wattage is fixed, this happens regardless of where you split the signal or if you use a fuse or not. most in car systems can have the ignition run line drop as low a 6 volts (some as low as 2.5 volts) and they still operate. It's not a power line, it's basically a binary switch line meaning "I'm in run or I'm not." You an have very crude logic there as long as you have a hysteresis (switch on at 4 volts, switch off at 2 volts) for example.

The BCM is behind the passenger foot well (and the glove box). I'd just tap the source.
02-03-2017 08:31 AM
firebirdude
Quote:
Originally Posted by MK3 ST3 View Post
I never understood the idea of an add a fuse. Usually when the radio goes in you can hijack enough of it's wiring to not have to run additional leads. I've never done the Focus but historically I've only needed to tap things like a "switched ignition line" and an "illumination line" both of which don't need to be fused.
Maybe I'm misunderstanding you, but they're wiring up an ignition lead to the head unit because there's not one from the factory on the MKIII Focus....and they're too cheap to buy the proper module. lol So I'm not sure what you'd hijack behind the head unit to not run an additional lead?

If the wire you're using the tap in cannot carry the amperage (gauge vs length) of the factory fuse, you need to add your own fuse; be it an add-a-fuse, in-line fuse, etc. Running 16-18awg wire on the factory ignition circuit certainly requires its own fuse.
02-03-2017 05:28 AM
MK3 ST3
Quote:
Originally Posted by CFHGARZA View Post
I used those before but I prefer the kind that add a fuse too.
I prefer to just use blanks (if possible some of them are wired up). But that's only if I really need an extra circuit.

I never understood the idea of an add a fuse. Usually when the radio goes in you can hijack enough of it's wiring to not have to run additional leads. I've never done the Focus but historically I've only needed to tap things like a "switched ignition line" and an "illumination line" both of which don't need to be fused.
02-02-2017 07:30 PM
firebirdude
Quote:
Originally Posted by rczrider View Post
I'm dumb. I didn't even realize that the kit from Spiral included a fuse tap because I didn't recognize it as such

Additionally, that type of fuse tap is not recommended because forcing another fork into the factory terminal spreads the terminal out more. If you ever remove the tap, the factory fuse may not hold as tight.
02-02-2017 02:59 PM
CFHGARZA I used those before but I prefer the kind that add a fuse too.
02-02-2017 08:34 AM
rczrider
Quote:
Originally Posted by CFHGARZA View Post
There is a little panel that is held on by two plastic squeeze caps under the glove box.
Any auto parts store will have the fuse taps aka add a circuit or Amazon.
I'm dumb. I didn't even realize that the kit from Spiral included a fuse tap because I didn't recognize it as such

01-30-2017 02:52 PM
CFHGARZA There is a little panel that is held on by two plastic squeeze caps under the glove box.
Any auto parts store will have the fuse taps aka add a circuit or Amazon.
01-29-2017 06:28 PM
MK3 ST3 All Fords have a switched ignition line. It's called the "Ignition/Run" line in wiring diagrams. I have my radar detector spliced into one that goes to my sunroof.

I know this because the EPS uses it to wake up the ECU and start providing assist. It comes from the BCM, so if you can't find a place on cars to tap into it, always go back to the BCM.

There is also a CAN signal, and a lot of "non-critical" modules (like the stock radio) use that.
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