Yes, it was a single nut holding a stainless back plate. So, I took the solenoid off its mount on the reversing valve and felt the "hole" energized when selecting heat at the SMXII controller. Read elsewhere in here that its either "yes or no" on the magnetic field, no weak or strong. Is this correct? Guess this means the reversing valve is stuck. Tried banging on it to no avail. Any hope? How long should it take for it to produce warm air? Maybe I'm not giving it enough time.