i'm not sure where control unit is if in evaporotor assy or on outside of cab in rear of cab like 8010's, was on cnh web site, shows breakdown of all a/c, there is a probe that goes into evaporator, they have caused issues, will not let a/c kick in if bad, i used to work for case dealer as a tech, afraid your gonna have to git a case tech out to see whats going on, system isn't that difficult once you understand how it works, took me a while on first machine, lots of reading service manual, found that service school books were much more helpful, gave ohms for sensors, i will make a call at dinner time talk to my buddy, we have had very few issues with these machines, 8010's had some issues, mostly darn heater control valve, scott.