Switched 12V under hood - where?

Rdonahe · Dec 3, 2011

I must be dense because I'm searching high and low and can't find the answer.

I need to find a switched 12V wire under hood to tap into. Preferably one that is only live when the ignition switch is in the ON position.

Other threads reference running off the PDC but I'm unclear how without tearing it apart. All the blank spots topside on the PDC are dummies, there are no terminals to access underneath.

Thanks in advance,
-Roger

Tim_MN · Dec 3, 2011

Buy a $5-12 volts/ohms meter at the hardware store or big box home improvement store and probe for 12 volts when the key is on. It is simple enough to run a wire from the interior to under the hood, just poke a hole in any of the existing rubber wire boots or grommets.

Rdonahe · Dec 3, 2011

Tim_MN said:
Buy a $5-12 volts/ohms meter at the hardware store or big box home improvement store and probe for 12 volts when the key is on. It is simple enough to run a wire from the interior to under the hood, just poke a hole in any of the existing rubber wire boots or grommets.

Yeah, that's what I'll do if I can't find something under the hood. I'd rather tap into something closer though, there's got to be something accessible.

I've got a multimeter, problem is most of the wiring is is hidden inside of wrapped harness/bundles and not very accessible.

O-Gauge Steamer · Dec 3, 2011

It would help to know the year...

Generally speaking, the Dark Blue with White Tracer is powered during ignition and start but not accessory. Leastways on 97 up XJs and the 93 YJ I recently wired...

old_man · Dec 3, 2011

How much power are you needing? The wire to your radio should be switched power. The color depends on the year.

ehall · Dec 3, 2011

How much juice do you need? There are a bunch of wires in the PDC and computer harnesses, and you could use those to drive a relay into the constant 12v main, providing you with "switched" power

Rdonahe · Dec 3, 2011

ehall said:
How much juice do you need? There are a bunch of wires in the PDC and computer harnesses, and you could use those to drive a relay into the constant 12v main, providing you with "switched" power

Sorry should have put this info.

It is a '98. I don't need much juice at all. I'm installing a second battery with a solenoid to break the connection when the Jeep isn't running. I have 4 gauge wire running to the solenoid for the actual charge circuit. This is just the on/off signal for the solenoid so it will close and complete the charge circuit when the Jeep's running.

Rdonahe · Dec 3, 2011

o-gauge-steamer said:
It would help to know the year...

Generally speaking, the Dark Blue with White Tracer is powered during ignition and start but not accessory. Leastways on 97 up XJs and the 93 YJ I recently wired...

It's a '98 (I should have put that in the original post, sorry) and this is exactly what I'm after. It's the on/off run to a solenoid for a second battery, not the actual charging circuit. I do not want it connected when the key is in the Accessory position. Only in the ON spot. I'll see what I can find in a dark blue with white.

Thanks.

Eric96Xj · Dec 3, 2011

both the interior and underhood fuse panels have blank spots in them that can be tapped into. many of these spots do get 12v power when the ign is on, like mentioned get a voltemeter or a test light at least and poke in there to find one . run a wire out of the fuse box and your ready to go . just make sure you use at least an inline fuse or better yet a simple relay with what ever your doing so you dont start any fires.

Rdonahe · Dec 3, 2011

Thanks guys. I ended up tapping in under the dash and ran the wire through an existing grommet in the firewall. Wasn't my first choice but in the end it works fine. Problem solved.

Switched 12V under hood - where?

Rdonahe

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Tim_MN

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Rdonahe

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O-Gauge Steamer

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old_man

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ehall

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Rdonahe

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Eric96Xj

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