What to Do When Car Generator Voltage Is Low?

[JosiahFitz]

Remove the plastic cover of the generator and use a multimeter to measure the six (or eight) diodes of the rectifier bridge. The three small diodes used for excitation also need to be measured. The resistance of the 28V generator excitation coil should not exceed 15Ω. If normal, proceed to the next step. Use a multimeter to measure the resistance between each of the three phase lines and the neutral point (N). The resistance values should be equal. If one shows significantly higher resistance, it indicates an open circuit in the coil. If all the above checks are normal, remove the plastic cover to locate the regulator and replace it with a new one of the same model.