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Help: What's the easiest way to hardwire into ACC +12V?

5489 Views 10 Replies 7 Participants Last post by  hijax2001
I have a need to attach a thin (20-24 ga?) hot wire up to 12V switched accessory source. The (+) wire that will be attached has an inline fuse. There is also a ground wire.

The cable is running down the left side of the dash. It would probably reach over to the driver's side too.

What's the easiest way to accomlish this?

I've seen the fusebox with it's itty bitty fuses (and no puller?) Is there a way to plug in or do I have to strip a wire behind?

Or should I go over behind the passenger dash and attach to the accessory socket?

It's for a Wayfinder V7000 Compass/Thermometer/Barometer/etc.

Thanks!
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[quote:3b2c7c67a5="Einstein"]I have a need to attach a thin (20-24 ga?) hot wire up to 12V switched accessory source. The (+) wire that will be attached has an inline fuse. There is also a ground wire.

The cable is running down the left side of the dash. It would probably reach over to the driver's side too.

What's the easiest way to accomlish this?

I've seen the fusebox with it's itty bitty fuses (and no puller?) Is there a way to plug in or do I have to strip a wire behind?

Or should I go over behind the passenger dash and attach to the accessory socket?

It's for a Wayfinder V7000 Compass/Thermometer/Barometer/etc.

Thanks![/quote:3b2c7c67a5]

You'll need a test light. Here's the procedure I'd use:

1. Open the hood and remove the lid to the fuse box.

2. Read the inside of the fusebox cover, it has a diagram of what the fuses are for. The diagram will also show you where the fuse puller is.

3. With the car off and key removed pick a fuse that would withstand the extra load introduced by your accessory (even though it has it's own fuse).

4. Test the fuse for power, if it has power, it's constantly on, avoid that one and move on to the next fuse. Continue procedure until you find a few fuses that do not have power in the off position.

5. Make sure all existing car features are turned off like AC, wipers, radio, etc. Turn key to ACC and use test light to check the fuses you selected in step 4. Make note of any that are now lit, eliminate ones that are not and move on to next step.

6. Put the car in the next key position but do not start it. Make note of any fuse that is still lit, eliminate ones that are not and move on to next step.

7. Start the car. While running, check remaining fuses. Make note of any fuse that is still lit, eliminate ones that are not and move on to next step.

8. Turn off the car and remove the key. Double check the fuse(s) you've selected now have no power.

9. Find a wire underneath the fuse box that you believe connects to the fuse you selected. Check this wire with the test light just like in steps 4-8 above. If confirmed, this is your wire!

10. Run the wire for your new accessory through the cabin, behind dash and through a firewall grommet. A shop light and a friend are handy for shining the light into firewall grommets from the other side so you can see where to poke the wire. Run the wire all the way to the fuse box.

10. Get yourself a wiretap connector at the hardware store like the one in the picture below...



11. Place the wiretap on the fuse box wire you chose and slide the new accessory wire into the wiretap as well. Close the tap and use your test light to check for juice on both sides of the tap as well as the new accessory wire. If all is well, use some electrical tape around the wiretap and use some zip ties to secure the new power wire all the way back to your accessory.

If all went well you'll now have a reliable power connection that turns off automatically with the key. :D

P.S. You can use the accessory socket by pulling dow the panel under the dash with the 2 knobs. and reaching in from behind. I'd still use the test light to ensure I had the right wire.
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Einstein,

Please post pictures and lessons learned after you are finished. I am considering the wayfinder and am curious as to where you put it and how you mounted it.

a-T-d-H-v-A-a-N-n-K-c-S-e

-Chad
Actually, the Wayfinder doesn't tell you whether to hook it up to ACC or BATT.

From what I'm inferring from the owner's manual, my new understanding is that you are supposed to hook it up to BATT, then it automatically turns on when the voltage jumps up because the alternator is turning (engine is running).

I'll be wiring it up tonight directly to the battery to verify this is the case. If it works out, I'll be looking for a constant battery source instead of accessory switched.

P.S. I have terrible success with wiretap connectors, especially when the wires are not the same gage!
At the end both of the (+) and (-) wires, I soldered a color-coded mini alligator clip.

I sent the wires past the door frame, behind the top of the fender, and to the battery (about the same path as the temp sensor, but that made it the whole way to the front bumper.

I attached the clips directly to the battery screw threads, there was plenty of room for the red cap to close over the insulated alligator clip. The inline fuse is only about an inch from the battery, so I don't expect to have any safety issues.

The slack wire was wrapped around the wire bundles located between the hood hinge area to the battery.

So far the unit is working like the manual says... Hooking up to a constant power source seems to be the right answer. I'll let you know if I find out otherwise.

The wayfinder is attached at the top of the windshield, between the rear view mirror and the sun visor. The wires from the unit down to the dash area were all pushed behind the trim (no disassembly required)

I plan to add a strip of 20% tint across the top of the windshield to help keep the direct sunlight off of the unit, and make it more readable (darker surrounding the unit). I wanted to do this anyway, ever since getting the window vent visors. Plus cops won't think there is a radar detector there when they see suction cups!

As for the wiring, I might just leave it the way it is forever :D But seriously, some COOL day when my back doesn't hurt, I'll get under the dash and do the job "right".

:!: Special thanks to eMass for his detailed description of how to find the right hot wire and connect it without much fuss! This may come in handy later. To overcome the AWG mismatch, I might have to solder a piece of thicker wire to the skinny one provided, then it might work in the tap device...
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1. Open the hood and remove the lid to the fuse box.

2. Read the inside of the fusebox cover, it has a diagram of what the fuses are for. The diagram will also show you where the fuse puller is.

3. With the car off and key removed pick a fuse that would withstand the extra load introduced by your accessory (even though it has it's own fuse).

4. Test the fuse for power, if it has power, it's constantly on, avoid that one and move on to the next fuse. Continue procedure until you find a few fuses that do not have power in the off position.
I checked this before and never found a fuse that was not always hot, with or without the ignition.
For those interested, I also had success installing the 5" windshield banner tint.

Look for the post showing the tint HERE
Send pictures to me. I will post 'em.
Thanks to isketerol, you can view the installed wayfinder HERE
I got two of these with my 12volt extension. Not sure how or when to use it but I would like to hard wire my extension in.

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I see that Fuse #18 on the interior (under the steering column) is a strong 15-amp source and is also what runs to the "Accessory Power Socket" - though I'm not sure which one...

I guess that should be a hot-only-while-the-ignition-is-on source, and definitely has lots of juice.

Any further details on whether this would be a good source to tap into for another aux 12v cig outlet?
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