We have a lp water heater.have replaced the temperature control valve & thermocouple.
The burner comes on & stays lit for a few minutes then goes out. Then if turn up the temperature it will run again for a few minutes & then kick back off. Pilot light stays lit and never goes out.

Are you saying you replaced the gas valve? Or do you have a commercial unit with an aquastat?
Can you tell us the make and model of the water heater?

More info. Needed, for sure!

How old is the water heater? Is it a closed combustion chamber (bolted door over the combustion chamber)?

How about LP supply? Does the LP gas only supply your water heater, or does it also supply the boiler/furnace or other appliances in the house?

Let us know more...

Mark