there is a large vent at the front and it goes directly outside, there is a small aluminun filter on the outside. In the colld, the air flows into the cabin with no resistance, what is this for and why? Is there a way to block this off?

thanks In advance

Al Venditti wrote:

Do you have a picture? Is it above your Onan Generator?

I will take a picture when I am back with the unit. It is the big vent behind the opening under the radio. And above the onan is an aluminum filter the leads directly into the same vent in the cab,

Rick

My 2018 35D has the same vent hole, but i have a paper style air filter covering it.  The factory shipped this filter with the coach, but it was not installed, was just hanging by a tie wrap above the Genset,  in the front bay.

Yes, cold air was coming in on our first trip, that when we discovered it. 

A mystery for sure why its even needed.