weather conditions? only reason i ask is, i had a similar issue with the stereo (aftermarket). but we know how well that vent in front of the windshield likes to swallow up water and its sealed oh so well. small drip made it inside, got the stereo wet, silence...... bout 5-10 minutes later im guessing it dried up enough. rock on.
so i made a lil roof under the dash, over the stereo, to hold me over till i can find the leaks source.
hasnt done it since.
im not sure how the speedo werks in the later model jeeps, elect or mech? if elect. you may end up under the rig tracing back up to the box under the dash from the transmission. but since both the speedo and bags went out.....id start under the dash. look for broken or worn down, shorting wires, and for moisture on or around control boxes. stop the leak or seal the the control boxes?
i dunno? long post for not even being sure if it was raining or not when it happen'd.