I have inherited an old VC Resolute I and am ready to begin using it, but the thermostat control doesn't seem to be working. I understand that the coil automatically regulates the air inlet, but I've also read that I should be able to set the level to keep the flapper open or closed. I believe I have all of the replacement parts, but am not sure if I have it all reassembled correctly. What am I missing? Finding a diagram or video of how to reassemble this is impossible!