Window A/C unit in the rear door

[arctictraveller]

I'm sorry to report that my great idea of putting a home style window A/C unit in the rear door has been a failure. The first one I installed failed after one trip, so I bought a different brand and tried again. Last weekend, while at a motorcycle race, temps reached nearly 100degs, so I fired up my Honda gen and was looking forward to watching the races from the comfort of my (cool) van. No luck. It seems the second unit failed just as the first did, no doubt due to a few thousand miles of rough British Columbia gravel roads a couple weeks prior. The unit worked once during that trip but I never tried it again until last weekend. I refuse to give up though, as I'm in this project over $1000 so far (mostly the cost of the gen). I'm guessing all the vibration has cracked one of the copper refrigerant lines as the home units are normally stationary and not subject to much vibration. The last two units were hard mounted, perhaps some sort of shock mitigating method would help, or I imagine if I stayed on paved roads it would survive, but that's not going to happen. Any other ideas?