I have a lennox central unit, for about a 2500 sft. house, the filter light was on and the battery light flashing when we noticed the unit not cooling the house even though the fan is running. i reset the thermosat and put new batt. in it, checked the breakers and the fuse by the condenser, everything as far as that goes is good, i dont know what else to check, and my ac man is of course, unavailable...could you please help me?