After researching mixing valve problems on the web I had the cartridge replaced in the Moen single handle shower valve to increase hot water. The hot water is known to be available by the sink next to shower where it is very hot. The new cartridge did not produce any more hot temperature than the old (2.5 years) one. Seeking a solution I removed the stop for the rotation to see if more hot water could be found. There was a burst of very hot water for a brief (.5sec) without changing handle and then a return to just warm water.
This suggested that a thermostat was kicking in to prevent scalding when water is too hot. So I lowered the temperature from the tankless heater but it did not improve the condition. The research said these thermostats sometimes use wax pellets that control temps. Question..is the thermostat located in the cartridge? If not where would it be? Question=85what other possible cause is preventing hot water reach shower head? thanks Bill