I have replacd the fan control center in my Rheem 080a furnace, How the fanwill not shut off in the "auto" mode and the fan will not run in the "ON" mode. All wiring is by the diagram on the furnace. Replace the thermostate 2 times.?

Does furnace come on in the"Auto" mode when thermostat calls for heat?

Yes the fan also runs when the thermostate is removed from the wall plate

Not a heating tech but fan should not run with thermostat is removed.

Still sounds like defective fan relay. If relay is separate unit you can probably replace. Trace fan wiring backwards. Does wiring go to relay or control board?