How to repair a Pentair Mastertemp Heater

This is a lengthy but well edited and thorough video on multiple, very common problems I find on a master temp heater. All on one heater this is a very useful and educational video, Especially for professionals in the field but a DIY can also use these these tips for their own analysis but I advise hire a professional!

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I have a Pentair mini max with 8.88 flashing. Put in a new pressure switch and temp switch and and the 8.88 is gone but now just says err. Still will not come on? Suggestions?