Pulsating Alternator Gauge

Sooner or later that gauge, or that circuit, is gonna make trouble. The best solution I have found is to bypass it completely. Out of sight is peace of mind.
If your system dies, you will know it only slightly later than if the gauge was still working;
It's kindof like when you lose oil pressure at WOT, The gauge doesn't tell you the oil pressure is gone; rather the chit going on under the hood does. Then you look at the gauge and see what you already know.
Or like when you blow a coolant hose; the steam tells you something is wrong. Then you look to the gauge to verify what you already know.
So it is with the Amp gauge. You look there to verify what you already know.

If the amp gauge does this only in one direction, then you may have a short in that circuit.
If it does it in both directions, then your charging system may need a look-see.
If your car has an electro-mechanical regulator it could be completely normal.
If you have a post 1971 Mopar with an electronic regulator, the gauge could be telling you that the charge-circuit needs attention.
Happy HotRodding.