Accessory Wire Under Hood 2004 Expedition

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Forum Name: Vehicle Wiring Information & File Requests
Forum Discription: Request Car Alarm, Car Stereo, Cruise Control, Remote Starter, Navigation, Mobile Video, and Other Vehicle Specific Wiring Info, Manuals, Tech Tips
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=72690
Printed Date: May 11, 2025 at 4:01 AM

Topic: Accessory Wire Under Hood 2004 Expedition

Posted By: bravesirrobbin
Subject: Accessory Wire Under Hood 2004 Expedition
Date Posted: February 12, 2006 at 2:26 PM

I have a 2004 Ford Expedition and need to install a self made X-10 Car Sensor under the hood. I need to know where I can tap an accessory voltage source (+12 volt when the vehicle is running, no voltage when the vehicle is turned off). I searched for this information and noted it contained wiring harness information color code, but I'm not sure where this harness is (or if is is) under the hood. Any location under the hood will do as I plan on installing this unit behind the front grill.

Thanks in advance as this information will greatly help me!

Replies:

Posted By: bravesirrobbin
Date Posted: February 12, 2006 at 5:25 PM

I added some pictures taken under the hood of the 2004 Ford Expedition to show possible wiring harness locations:

Here is the general area under the hood. I circled one possible harness location to use:

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Below is a closeup shot of that wire harness location:

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Below is the "left side" of the engine where possible wiring harness locations exist for the accessory source. There is a two wire plug that is just sitting in a dummy receptacle (not doing anything) on the far left, but no voltage existed on any of those pins to ground when vehicle was running (anyone know what that does)?

posted_image

Below is a closeup of that two wire terminal:

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Hopefully one of these harnesses can provide a 12 volt accessory source. I will also place an in-line fuse where ever I tap off! Thanks again for any help.

Posted By: bravesirrobbin
Date Posted: February 15, 2006 at 9:22 PM

Wow, I didn't think this would be that difficult to answer. Does anyone know of anyplace else I could possibly find an answer to this question?

Posted By: dualsport
Date Posted: February 17, 2006 at 4:13 PM

I've never dealt with that specific vehicle, so I couldn't point you to a good spot. Probably no one else has either, or they would have chimed in. If you really want to avoid just running a wire through the firewall and tap off from something in the engine compartment, it may come down to just probing around until you find a likely candidate.
You can use one of those insulation piercing probes to minimize the damage done to the harness, but it may be safer to run a wire through.
Even if you do find something that looks like it does what you want, I'd isolate it using a high impedance circuit instead of connecting directly to your device, since you don't know what the signal's drive capability is.