Adding New AC System To 1998 Sundowner Sunlite 3 Horse Gooseneck Trailer
Updated 01/05/2026 | Published 09/16/2024
Question:
Good afternoon, I have a 98 sundowner sunlite 3 horse slant gooseneck horse trailer that has a 7 shortwall. I want to add a AC unit to the tack room. Currently there is nothing there other than a vent so I will be starting from scratch other than the hole. Which AC unit do you recommend? Will I need both 12v and 120v or will just 120v run it? Also I may want to add another AC unit to the back where the animals are for summer trips. I use the trailer to haul show animals for my daughters. Which package would you recommend for that area?
asked by: Brett H
Expert Reply:
Hello Brett, thanks for reaching out. To add a new AC system to the tack room in your horse trailer, I recommend the Advent Air RV Air Conditioner System # ACM135C. This is a complete AC system, so you get your AC unit, controller, start capacitor and manual control distribution box. Meaning the controls for the AC will be on the ceiling of the tack room as part of the vent assembly. 120v is all you will need to run it.
Keep in mind that the roof must be between 2-1/2" and 5" thick, so you may need to build out the roof slightly depending on thickness. Also make sure the roof of your trailer can support the weight of an AC unit (about 80 lbs). The # ACM135C AC system can be used in really any room in your trailer as long as it meets requirements. These AC units are made to fit the same standard 14"x14" roof opening as most roof vents.
If you are adding AC to the back of the trailer you may want to use a separate wall thermostat, so the Advent Air RV Air Conditioner System - Single Zone # ADV94FR will be better suited for that. It comes with a distribution box controlled by a wall thermostat. It is the same 13,500 BTU advent unit as I mentioned above.
We have a few videos on this Advent AC system that you should find helpful, and you will find links to the videos just below. Feel free to reach out if you have any other questions.
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Jesse M.
1/5/2026
Hey Brett, how did the Advent Air system work out for your horse trailer’s tack room? Did the 120v setup give you enough cooling power for your trips? Your experience could help others planning a similar upgrade for their trailers.