My voltage gauge bounces between 12 and 16 while idling at startup. As soon as I give it gas, the voltage spikes to the max reading the gauge will read. This started happening after I cleaned the fusible links with a brass wire brush without disconnecting the negative battery cable. A spark shot from the link terminal through the wire brush into the bracket that holds the fusible links. I thought it was the voltage regulator that was fried in the alternator, but after installing a new alternator, the problem persists.

 

Sorry, the cars a 1978 280z.

 

Mosts likely it's your alternator preparing to go out.

 

Thanks for the reply but it's not the alternator or voltage regulator. As I said above, even after changing the alternator, the problem still existed.

 

Are you sure you got an internally regulated alternator? The 70-77 S30's use an external voltage regulator.

Simple solution: drive your car to your local parts store and have them do a load test on your alternator / battery.

FYI: Parts store reman alternators for the Z are notoriously duff.

 

Yea it's definitely an internally regulated alternator. I took the original alternator to autozone and it passed all three tests. What else could cause the voltage to spike uncontrollably in spite of a good voltage regulator? Or better yet, what would cause a good voltage regulator to misbehave?