When we travelled cross-country last summer we ended up leaving our dog in the cab of the truck with the truck running and AC on. We locked the cab of course. Didn't run into any problems with the truck overheating.
2012 FunFinder X 210UDS
4-68 watt flexible panels; 1-215 glass panel/4 Battle Born LiFePO4 Deep Cycle Batteries
2014 Ford F350 6.7 Liter PowerStroke V-8 Diesel longbed, SRW