First ask from Perkins the user manuel. It is a must to have and a fault likethis is in it trouble shooting guide. second check that the main braker fuse is on. ????? third check that if you use one phase that the controller is setup as one phase and not 3 phase.
You didn't state if this occurred in no-load, hi-load or all the time. if this is an installation that has been installed for awhile and functioning normally in the past you want to verify that it is getting proper fuel and air. Clogged fuel or air filters can diminish power output. Check that fuel supply is proper and clean fuel. In general low frequency problems are low engine power related and specifically low RPM. If the engine has high wear it may be gradually loosing power over time, in that case you can prolong it's usefulness by increasing high RPM limit at the governor. In that case you may think of it as a warning flag that the engine will need overhaul or replacement sooner rather than later.
