Have a couple questions about my heat pump. The hp is a ruud upql-030jez with a rgtm 070erbgs gas furnace. on saturday sometime while i was away from home the heat pump quit running. I am getting codes l23, and 28 out on the hp. I had the installing contractor come look at it today and he said the filter was dirty. the filter is a 3 month old 20x20x5 filter which according to him should last 12 months. would the filter cause this or is there something else going on?