We have two MasterTemp 400 heaters heating an indoor junior Olympic sized pool. The pool was resurfaced in September of 2013 and since that time we have had problem after problem with our heaters - one of which I have since replaced. One of my heaters is 2 years old and the other I purchased in October of 2013. The trouble we are having is that the heaters won't run consistently. They shut off at different times of the day and night. The service heater light comes on but there is never an error code. One heater may keep running and the other shuts off. We have had all the plumbing redone and installed flow meters so we can monitor flow. We thought this repipe job would fix the problem but the heaters still continue to shut off. We had new gas lines ran with regulators for each heater but this has not fixed the problem either. We have had ignitors replaced, thermal regulators replaced, heat sensors replaced. We are at a loss. Anyone have any ideas? HELP!