A few weeks ago my heater started acting up. It will blow warm air for a few minutes, then it will blow cold air for a few minutes, and then repeat the cycle all over again. Sometimes it will do this while sitting at a stop light, sometimes it will do it while driving. Being that I live in the frozen Hell known as Fargo, you can imagine that this presents a problem for me. I replaced the thermostat back in November, so we can rule that out as the problem I believe. Anyone have any suggestions?