07 - 9400i AC not blowing in sleeper

I have a 2007 International (9400i). The front blows cold air nice and strong but the rear doesnt do jack crap. sometimes it comes on and blows for a few minutes and then nothing. Ive checked the relay and fuses up front in the fuse block and they are fine. Anybody know what the problem could be? And or how to fix it, things to check etc? Thanks. I try and do most of my own work, but this is the first time i have encountered this problem. Thanks for any advice.

 

i looked, and all i saw was a few fuses that were labeled ECM and something else. Ill have to revisit that area. Thanks!