I'm so proud of myself! Tonight my furnace suddenly stopping working and wouldn't light. Since I knew nothing about how furnace works, I went to the Internet and search information about how to troubleshoot the problem. Following the instruction, I confirmed that the thermostat is set right, the pilot light is good, thermocoupler is good, transformer is good, the last thing would go wrong would be gas volve, which is expensive. However, I didn't give up and I studied the electric circuit of my furnace. I found there is an additional component "vent safety sw" in between transformer and gas volve. I guessed it should be a safety switch but I didn't know how to make sure it is good. Thus I turned off power and used multi-tester to test it and found the circuit was open, then I used my hand to probe and found there is a small button could be pushed. I pushed the button and the circuit became back to close. And the furnace is working again! Good Job, Samuel.
