I bought an 03 Rubicon and the rear locker light blinks when i try to enguage.  The front lock right up with no problem.  I hear the component underneath the body on the skid plate running like it is trying to enguage.  What should I be looking at or if needed take apart to lock the rear.  

it'll run fora while then give up if it doesn't lock.

check for pinched, broken or a disconected line.

there's a separate pump for each locker, the one on the left side is the rear pump, be sure the lines are intact, they are easy to break off of the pump,especialy if ya back over a pile of brush or tree with limbs sticking up... as I've had happen.

the intake has a "T" in it connecting both pumps, the main line goes up out of harms way and prevents it from sucking water.

one other thing.. it yer parked it won't lock untill ya roll forward or backwards a bitt

the wires that plug into the diffs are only for the Idiot lights on the dash.

ya can pull the intake line to see if it's sucking air,
be carefull if ya pull the small presure line, the tits are easy to bust off while checking the presure, it'll have about 7psi. if it's got presure ya have a leak for sure. I haven't seen one yet that's messed up inside the differential.  

here, I painted a picture for ya....

 

Ya have it shifted into 4-low right?  

LOL, I didn't even think of that cappa... though it was mentioned the lights were flashing... they won't in high.  

Accually I did the mod, but yeah, even b-4 the mod it didnt work, Imma go check the lines, Ill let ya know what I see, Ill even take pix for ya IF i cant figure it out  

Yup, I checked the3 rear pimpkin and I saw what looked like a niple so i looked arround and whaddya know, i found a dangleing line. now, ther is mud/dirt in the nipple of the rear, should I clean it out and if so, whats the best way?  

suction....

pinch the hose further up the line, use a squirt bottle with soapy water, suck it out..

if its the compressor that has mud in it remove them so ya ca clean it out, same way, and wd40.
just dont use it on the hoses, they can swell.