Hi guys, new to this forum and posted on the wrong side. I am a lic. plumber but not so experianced on repair. I got a gas water heater to repair tomorow. h/o said he replaced therma couple it lights but when he turns knob to let main burner come on it goes out. If he lets it sit on pilot mode it continues to burn. Im thinking if this is what it does when I go look that it must be the control valve needs changed. Any input?