Why does bunner light then runs for a minute shuts off then shuts off

Sounds like a faulty pcb,

The thermostat shuts off the main burner.The pilot light gas is controlled by the thermocouple which the side of the pilot flame has to envelop. If the flame is too small or too far away from the flame, it shuts the gas off to the pilot. The thermocouple generates a small voltage which keeps the pilot gas open. It can over time fail itself, so look at replacing it. The thermostat sounds like it's failing too.

Fan will come to dissipate any heat build up in heat exchanger

Check gas control valve.

Good luck,

Marty

Take a multimeter or 12 volt test light and probe terminals on Therm & ECO for 12 VDC power while running. When it shuts down and wateris not hot, test for voltage again at those terminals, If you have 12 volts to side of therm that goes to ECO beside it, then therm is ok, but then check opposite side of ECO as well. If power on one side of ECO, but not the other, the ECO is faulty. Simply walk across with probe testing for voltage when you find no power at one terminal but not the other, it's faulty, replace it.

pilot light keeps going out! more then likely its the thermal coupling doing this. if bad it shut all gas to heater for a safety measure. just shut power off, then turn gas off and replace it. then you should be ready to go. to relight heater hold down on gas vavle knob in the pilot position, hold down and light it at the coupling where gas comes out. when it is lit, continue to hold down for 60 seconds. release knob very slow. then if its lit, turn to the run position. if flme goes out, wait at least 5 minutes to expel the gas fumes and turn to pilot and try again. good-day !

your unit is undersized or you do not have enough gas supply to run the unit properly.
If you have to many water features running or you have to many gas items turn on at the same time it can cause problems.

water heaters run until they reach a certain temperature and then shut off, in a similar way to the thermostat in your air conditioning.

have service completed