My heater turns on, but it never shuts off. We have to do it manually. I'm hoping to fix this problem on my own. After I shut off the gas to the valve, can I just take the thermocouple off and buy a replacement somewhere? Or should I take the whole valve off and replace the whole thing? I probably shouldn't be so cheap and should just call a repair guy to replace the dang valve, but I'd like to try it on my own! I enjoy your show.