Observational data from the X-ray through the UV and optical of variations of the NGC 4151 nucleus were compiled. The characteristics of the variability related to the 1989-1996 cycle of activity show remarkable similarity to those of blazars and do not contradict the supposition that this cycle of activity was caused by a synchrotron jet (SJ). Some of the activity of previous cycles were interpreted in the framework of a SJ model and some of that of a disc instability model (DI). We ask the question if different cycles of activity can be of a different nature caused by a different accretion rate.