Just installed a lochnivar water heater,90% plus power vented. I'm getting a code for the FV sensor saying it sensing combustible fumes(gas leak). I have checked the mechanical space and there is no gas leak. While changing the furnace (oil to gas) I spilled some fuel oil on the ground. Could this sensor be picking this up? I tried to reset the water heater by unplugging it and even ohmed the sensor. It's DC voltage and I'm getting about 5 vdc to the sensor.. Any ideas? Bad control valve maybe?