I have a State hot water heater that the pilot light goes out when the water heater shuts off the burner. I have replaced the thermocouple and pilot light is okay. I am thinking that it is the thermostat? Needs Help.
This is one that is difficult to know for sure. Since you said ‘thermocouple’, there is not a lot that can be wrong, but the cause is sometimes difficult to pin down. Because a thermocouple does not create much power, any resistance in the wires of the circuit can cause flame shutoff. The wires must be in great shape and the contacts of the controls must be clean. Another cause of pilot outage is the size and shape of the flame on the thermocouple. If the flame strays because the main flame shuts off with a resulting flame movement, the heat on the thermocouple may not be enough to keep the pilot gas valve coil pulling the valve seat open. These problems need careful observation.