I am currently troubleshooting my heater and hit a stuck point. I have a Pentair Max-E-Therm 400 installed approximately April 2012. My pool is an in-ground gunite with attached spa (total approx 30,000 gallons). When I turn on the heater using either the spa or pool selection, the service system light turns on and nothing else happens. I have what I believe to be adequate water flow running through the system. No issues with the pump or filter at this time. Entire plumbing system has been leak checked resulting in no present issues. I have attempted bypassing the pressure switch by bridging the connection wires, but to no avail. The heater still does not fire. I have the spa set to heat to 100 and the pool set to heat to 90. Currently the water temperature is reading at 70. When I set the spa or pool temperature to heat at 70 or below, the service system light turns off. When I unplug either of the two sets of wires on the left side of the housing where the water inlet and output pipes are (I believe they are to a thermal regulator), The service system light turns off and the service heater light came on with an error of E01. Any help on the issue would be appreciated. Any help in regards to the issue at hand will be appreciated. Additionally, there was a point within the last two months where the pool had a severe algae bloom and the chemicals were all out of whack (Hurricane Isaac).