hi im trying to troubleshoot a problem maybe someone smarter than me can help. my gas hot water heater uses a bbq sparker. when the gas control knob is in the off position, i can see the sparker working thru the sight-glass window. but when i turn the knob to pilot and push it down, there is no spark anymore. i can hear the gas working, but it just wont give me a spark unless the control knob is in the off position. any idea what this means? thanks