My in dash voltage guage ocillates between 13 and 15 volts. This ocillation is very rapid approx. 1 time per second. When driving at night, the headlight, and dash light flicker at the same rate as the volt guage. The rate of the ocillation does not seem to very with engine speed. The ocillation sometimes goes away completely, and somtime lessens to only a 1/2 volt of fluctuation. I suspect the alternator is more than likely at fault. I have not have any issues with the battery not charging or failing to start. Has anyone seen this type of behavior? Thank you in advance if you are able to help.