A/C problem

First thing you do, is disconnect the Zone 2 remote sensor from the Board. That will make BOTH zones use the wall tstat for its sensor unless you also have a Zone 1 remote sensor. If the wall tstat is in a cabinet you will have a Zone 1 remote sensor. If the tstat is mounted on a wall inside the Tstat is the sensor. Regardless the Zone 2 will defer to the Zone 1 sensor. Then run and see if the Zone 2 AC operates at the higher temps(90 in the RV you set at 70 and it comes on). IF it functions correctly replace the Zone 2 remote sensor. The link shows the sensor and its cover. They also come in Black and brown, but odds are yours is white, Doug

http://www.dyersonline.com/dometic-ccc-and-ccc2-polar-white-20-remote-sensor-kit.html