Sigman is correct, the best thing you can do, is find some shade.
Depending on the size of your P'Up, you may want to see about getting one of those portable awning things, and park the trailer under it. You may even be able to make special fitting for the sides, that will hold the poles, in case there isn't enough height.
Even a smaller tarp or umbrella that will keep the A/C unit in the shade will help some....and you may want to even spray it with the water hose from time to time, to help cool it down.
Happy Camping:)