I have a 75 Gallon Natural Gas State Select Water Heater. Model # PR675NRVTZ. It has a fan on top that vents the gas to the outside. Normally, this fan only runs when the water is being heated. Now, the fan runs constantly eben when the water is not being heated. I do not have the wiring diagram, however I found a "switch" that if I unplug it will turn off the fan. The switch has 2 terminals. It has 4 screws that bolt it to what I believ is the gas valve. I ohm'd the switch out and it reads 0.00 (closed). Before I go and replace it, does anyone know if that switch is supposed to read 0.00 only when triggered and open line when not? If so, what triggers that switch and how can I test that other part? Thanks, Vin

Well you would assume that if "switch" is activated by the gas valve.by sensing gas flow pressure and closing the swith allowing the fan to run. If you remove the switch, never mind ohms... does your meter have a continuity setting (usually beeps loud when leads touch). With out gas pressure activated the switch, there should be "NO" continuity between terminal.. No ohms.. If you are reading 0 ohms the switch is closed and probably bad...