[w9det]

Referance my 2001 Safari 27 ft. 13,500 btu roof AC
That is what Dometic said, that if the wind gets the fan moving then a back draft will occure. I don't get any water or any other ill efects. Maybe if water does come in it leaves through the evaorator drian. In the summer on a very windy day I can hear and feal some slight air movement, which is a nice vent system. But in 30 degree or less weather like enroute Arizona etc form Chicago the air is unwanted. Especially you stop for the night. The trailer gets all heated up, walls etc. and now as you travel with no heat you have a draft. I assume it comes in during travel but don't really know but if it is windy, and it is quite often in the winter you can feal a deffinet issue.
I think it depends what way you are facing and if the fan starts moving, but there is not noice.