I replaced my Mattel toy fan that came with the HiLo when it was manufactured with a Fan-Tastic Fan many years ago and I think it was one of the BEST upgrades I could have done. The fan moves more air, it is quieter, it varies speed depending upon temperature and, the vent has a rain sensor that automatically closes and turns the fan off if it rains, meaning we can leave the trailer during the day with the fan on and not worry about a storm filling the trailer with water. It also uses less current than the stupid OEM fan!
It was a simple remove and replace installation, the fit was perfect in the existing opening and there were only 2 wires to connect as I recall.
Now, I have no idea what model I installed, since it was so long ago, but this one:
https://www.amazon.com/Fan-Tastic-80.../dp/B01LRF9PCA has all the features mine has. The model 3350 is almost the same, but it doesn't have the digital remote, which is handy since you can use it to control the fan anywhere in the trailer. I prefer having the remote.
Yes, it's expensive, but in my opinion, worth it! You may find this model cheaper from another source if you want to hunt for it.
- Jack