That is the first thing to try, because it is the most likely source of your problem.: My combination (instantaneous) gas waterheaters pilot light has just gone out. Im doing what the manual says ie. to hold down the : pilot light gas supply button, then press the ignition and release the first button after 60 seconds, but it just goes out again. Am I right in : thinking that the thermocouple is the first thing to replace before I spend my money on a more expensive part?: Andy