im hooking up an on board air system and Im trying to figure out a place that is switched on and off by the ignition, or could i get away with just going straight to the battery?

Only problem with that being is leaving it.. if there is any leak in the air system at all it will lower PSI and cause the compressor to come back on. obviously leading to an eventual dead battery.

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2003 limited 3.7L V6
Vader Edition

http://www.cardomain.com/ride/3219059

Use a add-a-circut and add it to the radio.

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Now: "07 steel blue JK Rubicon 2dr
4.5" Rubicon Express lift
rolling on 35"x12.5" Xtreme MT's
Warn M8000 winch
On board Air
Ham radios
Skidrow and kilby skids

Former: '05 Patriot Blue CRD. Lifted, locked, and a few other toys.

You want to get the power from the battery for something like that. Maybe use a relay that gets power from a switched source and let the relay power the compressor?

Not to sure where you could get a switched power source. Maybe the ACC wire behind the radio?

I dont believe the fuses on the side of the dash are switched.

Edit: W3CSX beat me to the radio.

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LOST KJ'S
Where are you going???
Current Jeep: 2004 Jeep Liberty
-Atlantic Blue
-Air Ride Rear Suspension ; OME/Rustys Lift ; Powertrax Locker ; Moog Lower Ball-Joints ; 245/70/16 Yokohama Geolander A/T-S's on MOABS ; Flowmaster 50 SUV
Lost #007082
http://www.cardomain.com/id/jeepjeepster

I agree with jeepster, run a your power through a heavy duty relay from the battery. The radio circuit should work fine to trip the relay, although there should be others?

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It may be that your only purpose in life is to serve as a warning to others.

06 CRD Sport
Built 5/11/06
Jeep Green
Rocklizard diff cover
V6 Airbox

I would first figure out how much current it will pull
then I would get a relay and hook it to a swichrd power sorce but not the radio if so you could get engine noise
I would look for an open slot in the fuse panel and use a male unsheilded crimp on spade type connector in that slot
and use that to turn on and off the relay

when you hook it up the way I found works best is to do it like this
swich in dash that gets power from ignition
dash swich powers pressure swich
pressure swich powers relay
relay powers compressor
I mounted the relay inside and ran a big ,fused, power lead from the batt to the relay
I grounded the compressor to the seat mounting bolt in the rear ,on a TJ

this way you have 2 ways to turn it off the dash swich or the ignition swich
and it will only come on when needed

I don't know if any of these will work on the liberty but here is where I have found switched power sources:

1) Radio
2) low coolant level sensor
3) PRNDL lighting (sometimes switched alone / sometimes activated by the lights)
4) Cigarette lighter (do all Liberty's have 2 12V power sources in the center stack?)
5) IGN box - pretty sure that one isn't applicable on the liberty

Definently run this through a relay

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02 Liberty Limited
Silver Outside & Taupe Inside
Heated Seats, Sunroof & Infinity speakers
USA Spec I-Pod adaptor, Mopar Sub, Garmin GPS
Tow Package, Select-Trac
Rock Rails, Tow Hooks