[kc98072]

I have a 13 3402 we used it a few times last year and a couple of times this year until 2weeks ago we've been full timing it. We are still getting small pieces of black foam (at least that's what it looks like to me)coming from both zone 1 & 2 Heater / AC vents... Is this expected? Anything I can do about it?
Thanks
Keith C
2013 3204 - 2013 Ford F250 4x4 6.7 Diesel