Originally Posted by ducksface
Pull off the panel near the fridge that allows you front access to the heater. On the lower left corner of the water heater you'll see a valve. Shut it all the way, open it all the way and settle somewhere in the middle. It's only a half turn or so.
That cured it all, every symptom you have, for us. Water wasn't being held in the heater long enough to stabilize heat. We now use only the hot water shower valve, no cold water. Not a single hiccup since we adjusted that adjustable valve.
It's a 30 second fix.
I have our valve set all the way open, no issues. It will get up to whatever temp we set it at. I like 103 and DW likes it at 106. All hot water, no cold.
To the OP, when you introduce the cold water, it reduces the water through the water heater. That can lead to the water heater not seeing enough flow and it shuts off. It is best to only use hot water set to the temp you like. The Oxygenics shower head is a nice upgrade.