Got any more details? Dometic Brisk Air, Coleman Mach? I'm assuming you have the analog thermostat? Regardless of outside temp, if it's hot inside, or the t-stat thinks it's hot inside, it'll run until it's satisfied. If it's an analog thermostat, it is possible that it's on the fritz. But, to answer the question, the AC should cycle on and off in auto mode. Have you tried bumping the temp up on the t-stat to attempt a forced shut off?
John and Rebecca Dickson
Emma-7 / Little John-5 / Iva-1
Full Timing Again, Rev B
2013 Ford F-350 Lariat CC LB PSD
2015 SOB TT - With OC's Awning Poles (#8)
At least in Heaven, RVs will be perfect, and I won't have to keep fixing them.