Just took the cover off the circuit board in the back. The black relay on the board is what is cycling and making the clicking noise.
The rumble comes from inside the box near the evap fan compartment and stops & starts over with each cycle of the relay on the board. Every two seconds.
I noticed it when I got up this morning and has been 5 hrs now, no cooling.
Its been happing the last couple months for about 20 mins in the morning sometimes in the evening, then stops.