I have a buck stove fireplace that was installed in a recently flipped house that we bought. The fire place appears to be new and has never been lit. The on/off switch was not even installed when I started messing with this thing to get it working. The pilot will light and stay lit but valve will not open to light burners. I checked the millivolt output with a meter and they were extremely low so I ordered and replaced the thermopile unit. I now get good voltage (500+ mv) when the switch that is 6 inches away from valve unit is off. When I turn switch on millivolts drop to 3 mv. What is the cause of this?