My exhaust brake started being intermitant about a month ago and when it is not working I can hear a clicking from under the hood. I suspect the solenoid - any one have the solenoid fail??

 

I just installed one on my 2006 and while I was at the Cummins dealer they talked about having a bad harness to the solenoid on one of their units.
Disconnect the solenoid vac hose and hold together with the one off of the vac pot on the exhaust elbow. If your brake now works you know the vac pot is good. Check your grounds, if you have a clicking you may have some loose wires and or ground.I still have my trouble shooting guide and can scan it if you need it. Dan