My plumber took a look at the pilot flame of my gas furnace which wouldn't stay on, and then said that it was either the thermocouple or the gas valve. He didn't have time to take care of it then. I measured the thermocouple with my multimeter and I got 0.2-0.3 V. The plumber on the phone said we need to make sure it is the gas valve, before purchasing a new because the dealer will not take it back if that's not the problem. There is no continuity between the TH-TH contacts, and no continuity between the PG-PG contacts (the gas valve is a White-Rodgers 36C03U, its manual says .750V, the furnace is probably 30 years old). As I was retesting the thermocouple, now I do not read a voltage on it either anymore, and I thought that because I've been handling (turn it in) the thermocouple and its wire I may have broken the wire. The thermostat circuit seems to be OK.
Are there any other tests I could perform on the gas valve to make sure it really is the culprit? What are the voltages that I should read from the thermostat? Any suggestion appreciated.