I have a Gas Water Heater and was just shipped a new Manifold Door. I have disconnected the 3 connections to the thermostat and taken out the two screws to pull out the old manifold door... But it won't budge. How do you get inside to see if the tubes on the inside are screwed into the orifice which in turn is screwed into the gas burner plate? There is no room to get behind the manifold door?

First, what kind / brand / type of water heater is it ? Please, provide us with this information so we can advise you further. Back to you. Milo