My heating system is blowing out cool air and I can't seem to find any info for how to locate the source of the problem. I have already resealed the duct-work with no luck. Furnace {inside} make and model info is ; E2EB-BL5HA made by Inter-therm by Nordyne/ outside A/C make is a Coleman Q.E.D. ll. I was unable to identify the model of the outside unit as it is greatly weathered.