The stability pot (potentiometer) on a generator AVR controls the nominal voltage target for the generator. The AVR will try to maintain the voltage at a preset level. If you need to adjust the voltage, you will may need to adjust this on the AVR.
How do you set the VOLTS potentiometer on a generator?
For setting the stability on an AVR, always refer to the manufacturers instructions. Some common AVR types are listed here. Some digital voltage regulators may have the potentiometer turned off in the software, so it may have no effect.
This is used for minor adjustment, if the alternators voltage is very low or very high, check the alternator voltage diagnosis section first. If you have another problem, adjusting the voltage on the AVR may do nothing, or could even damage the AVR.
Normally (again check the handbook) you only need to turn this very slowly, its normally clockwise to increase the voltage and anti-clockwise to decrease it. The AVR terminals are LIVE, so ensure you are qualified and take precautions, such as using an insulated screwdriver.