First you need to adjust the gas regulator, then the engine governor, then the full-load speed adjustment screw, then the voltage regulator pot. From my genset's diagnostic and owner's manuals (12kw Generac):
"It is important not to proceed until certain that
generator AC voltage and frequency are correct
and within the stated limits. Generally, if both AC
frequency and voltage are high or low, the engine
governor requires adjustment. If frequency is correct,
but voltage is high or low, the generator’s
voltage regulator requires adjustment."
"An adjustment potentiometer permits the stator AC
power winding voltage to be adjusted. Perform this
adjustment with the generator running at no-load, and
with a 62 Hz AC frequency (62 Hz equals 3720 rpm).
At the stated no-load frequency, adjust to obtain a
line-to-line AC voltage of about 252 volts."
You can get the diagnostic and owner's manuals from Generac's web site, in PDF form.
As a side note, I hate the oil pressure sensor on my unit. It uses synthetic oil, and with LPG there should be virtually no fouling even if the thing had 3000 hours on it. Mine has less than 100 after 4 years, so with a recommended oil change interval of one year I figure I can get away with every other year at a minimum. Nope - after a year, if its below freezing outside it throws a low oil pressure error just after it starts up. Runs fine after that if I manually restart it. The oil sensor is just too touchy when its cold, with year-old oil. Go figure.
