Originally Posted by Lyndajo
We have a 2006 Travel Supreme Fifth Wheel, model 40RLQ that we purchased November 2019. Other than a couple of minor fixes we have had to do we have only encountered a couple of problems. The front air conditioner (both are Dometic DuoTherm) has started to have a lot of moisture on the vents. This AC has 5 vents and only the 2 vents in the kitchen area are getting moisture. The back AC vents are not experiencing this. We are the second owners of this fifth wheel and have almost a foot of manuals and paperwork that came with it. Unfortunately I can not find anything on the AC system.
We live in South Texas about 60 miles from The gulf of Mexico so have lots of humidity.
Condensation on the vents - Lets start inside - Check the Filter for the return vent - good chance it's Dirty, restricting the air flow.
Second - turn the fan on so it is running all the time - not on the auto mode, where it turns off and on this will generally keep the vents dryer.
You will know if the exterior Condensation is working as there will be a steady stream of water coming off the roof when the A/C is running - which is likely all the time in South Texas.
Just like your Cold Glass filled with Ice gets wet the Cold vents if only experiencing limited air flow will get wet - so usually it's all in the amount of air and the Hmidity inside the Unit.
Best of Luck,
links that may help -