If you have a single AC that may be part of the problem. Another problem is the ducting in a Thor tends to be restrictive to air flow. I am including a picture of a simple mod to get better flow from the AC. On your inside cover there are usually two filters, one on each side under which are four screws that hold the cover on. One end of the AC is intake the other, usually the back, is output. Install the vent in the output end. You can use sheet metal screws since there is no strain, I didn't have any so I used machine screws. Hope this is helpful.
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