2008 Itasca Suncruiser - True-Air Heat Pump Fan Noise

I own a air conditioning company and have never refused to have my technitions work on RV, Repaired a few for my customers in the past. Actually, your basement air isn't much different than a heat pump for a mobile home. Others are right, your problem could be as simple as a loose or vibrating part or as serious as bad fan motor bearings but still easily repaired. Good luck.