Yep, sounds like a flow problem alright. The El Diablo has a safety system that will not allow the heater to fire up if there is insufficient water flow. If cleaning the flow switch (sometimes it needs to be replaced BTW) and/or the filter on your wand doesn't solve the problem, call Master Blend and talk to their service department. The guys there are great and will walk you through the steps you need to take to fix the problem.