With　the　extensive　use　of　room　air　conditioners,　their　refrigerants　have　a　greater　impact　on　the　environment.　Among　many　alternative　refrigerants,　R290　is　environmentally　friendly　and　energy-saving.　Furthermore,　the　dynamic　characteristics　of　R290　split　room　air　conditioners　are　different　from　those　of　HFCs　and　HCFCs　air　conditioners.　In　previous　research　of　R290　split　room　air　conditioners,　abnormal　system　parameters　frequently　occurred　in　heating　and　defrosting　process.　In　this　paper,　the　abnormal　phenomena　are　determined　to　be　caused　by　the　oil　blockage　of　throttle　component.　Especially,　the　failure　often　leads　to　safety　problems　of　air　conditioner.　In　addition,　the　abnormal　phenomena　of　a　R290　split　room　air　conditioner　was　reproduced　in　the　enthalpy　difference　chamber.　The　influence　factors　of　the　failure　were　studied　experimentally　and　the　experimental　results　showed　that　the　oil　blockage　of　EEV　are　mainly　affected　by　the　working　conditions,　the　type　of　lubricating　oil　and　the　opening　of　EEV,　which　will　provide　experimental　basis　for　further　mechanism　analysis　and　solution.　(C)　2019　Elsevier　Ltd　and　IIR.　All　rights　reserved.