Been sitting here reading old post for the past hour or so and learned a bit about the air ride but nothing really about the issue i am having. The rear is sagging, I found the coupling by the master cylinder broken. Replaced it, now the compresser is running and the rear bags fill up but want lift the rear. All was fine up until the coupling broke. The front is still up and it acts if the compresser just dont have enough psi to lif the rear. Not really sure which way to go from here. Thanks in advance for any help...........

 

Check for leaks in the rear bags. Soapy water in a spray bottle works well. I would check the lines running to the rear for leaks also.