frost on refrigerator coil

There are two evaporators on this model . If the fresh food is getting heavy frost build up the door may not be closing all the way or it could have a bad door seal. If this is not the case you could have a defective thermister # W10316760 . Or you may have a refrigerant diverter valve issue # W10331270. See video link below. https://www.appliancevideo.com/premiumotr/whirlpool-refrigerator-diverter-valve-reversing-valve-repair/

Matt Ace technician