Just to be clear, if you have your AC or heater set to the on position when you turn your engine on, you will hear the system purge until a closer temp to what you have set is reached. This will make a sound that is deep and low near the passenger side floor and if anything, it'll be more of a blowing sound.
If it's a rattling sound, it is likely your heating tubes located behind the glove box. If you remove your glove box and look behind, there are two silver pipes to the left. When cold they will rattle together and then stop once they heat up. The simple fix is to put something between the two pipes like a piece of radiator hose. I used a piece of old thick mountain bike tube.
Hopefully that's it. :thumb:
Good luck!
Can you hear it in side the jeep because you can only hear this in front on the JK?
Just to be clear, if you have your AC or heater set to the on position when you turn your engine on, you will hear the system purge until a closer temp to what you have set is reached. This will make a sound that is deep and low near the passenger side floor and if anything, it'll be more of a blowing sound.
If it is going away after warming up, I'd take 5 minutes (or less) and try the fix above. If it doesn't fix it, you've at least ruled it out. :thumb:
Another source to check if you haven't is JKF. I know there was some threads on the various noises back in the August/Sept of 2011 timeframe. If I recall there was a couple different sound issues with the 2012s, each with a different fix. Some more involved than others. :grayno: