Foul odor in basement

[Jeff & Deb M.]

Hello All,
We have a 2017 3920FB that we bought new in '17 and until this year, have only used it a few weeks out of the year. This April we retired and became full timers! We have always kept our Montana clean and well maintained, and other than a few small issues, have had no problems. But this morning we noticed a foul odor, similar to a dirty litter box coming from the air exchange behind the steps. I opened the hatch doors to the basement and the smell is stronger in there and seems to be the source. I removed a panel and shined a flashlight into the wiring/plumbing area beneath the bedroom floor, and don't see any leaks, but can tell I'm close to the source. Has anyone had this experience? Any thoughts on what I should be looking for? I plan to remove the coroplast tomorrow and look around under the rig, and hopefully can inspect the holding tanks while under there. Thanks in advance for any help!

[Montana Man]

Bang on the coroplast from underneath. If water is pooling, the coroplast will feel firm. If not it will give freely. Otherwise, a critter may have died in there. Good luck, let us know.

[Jeff & Deb M.]

Thanks for the reply Montana man. I did push on the coroplast and it moves freely, I didn't consider the critter theory though. I will be sure to search thoroughly when I have the coroplast removed.