I had a new gas hot water heater installed about 2 months ago. It was working, getting water hot, etc. A few weeks ago, I had a new furnace/ air conditioning system installed. Now suddenly, water gets lukewarm and stays warm, but will not get hot. Temperature control on unit is set for hottest setting. Checked pilot, power, all the basics, and can find nothing. Any ideas of what I could look for as a cause? -Maya