Thanks guys ! This IS a Fisher Pierce Sun tech , the date is 6/20/12 . The reason I asked is this P/C came with a new in box with a never used fixture . Must be a factory defect !
@ Ash : It only flashes the load at dusk . If you cover the cell , the it just turns on normally.
It is indeed a defect, Ash just describes the plausible technical cause.
If you cover it, there is not that strong light feedback, so the remained hysteresis (the relay mechanical hysteresis and finite gain of the electronic) is enough to make it seem to work OK. But ion the real life the feedback uses to be stronger, so the hysteresis has to be larger to prevent cycling.
If you do not succeed to claim warranty fix, you may open it, take detailed enough photos so someone here may redraw the schematic (e.g. me... ;-) ), reverse engineer its function and maybe pinpoint the possible defective components...