many ducted AC units have poor installation and can benefit from looking at the details of how they are installed. I found a piece of foam pushed out that sealed off the return and supply sides , the air was never getting to the coach it just went right back in the return path and short cycled 20% or more of the air. The hole was 14" wide and 1 1/4" the foam pushed out of. Both of my AC units had the same issue.
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