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hi i am dan i can help you with this. first lets start with how old is the heater and when did this first start
if you turn it all the way down does it produce the same water temp versus it turned all the way up
was the measured outlet temp exactly 140? did you test the temp rise from the heater
Hi my name is ***** ***** I have been in the plumbing field for 20 years. I will be glad to help you today. If you are certainly going to cancel your subscription that is up to you but I certainly can help with this issue. The problem is very likely a faulty thermistor or blockage in the heat exchanger. The blockage would cause the water to heat longer than it should and overheat the water and the high limit sensor would stop it from heating beyond the max. This issue could very well be solved by flushing the unit. If you are not familiar with how to flush the unit let me know and I will be happy to help with that too.
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