Code name “Baby”

[sternwake]

The voltage regulator is Internal to the Engine computer on Dodge Since '88

The Alternator is Externally regulated.

There is No separate unit even though the parts books will gladly tell you there is one.

A actual giant voltage spike would indicate that either the VR is fully fielding the alternator briefly, when the battery is already fully charged, and thus cannot accept much amperage, or the battery is losing connection with the alternator charging circuit, and the alternator current has no where to go.
The battery is basically a big filter and shock absorber.

You are not going to change its voltage super quickly, but if the battery is losing connectivcity with the charging circuit and the voltmeter is connected to that charging ciircuit rather than directly to the battery, you will see spikes when the battery is removed. Same reason why the old remove a battery cable from a running engine to check to see if the alternator is functioning is a super bad idea for any vehicle made within the last 35 years.

Another possibility is voltmeter error or Electro magnetic or radio frequency interference screwing with the voltmeter's sense wire, and If your phone happens to be near the voltmeter, try moving it away.

I'd Suspect the voltmeter first, but definitely double check the battery connections and make sure the alternator body is electrically grounded to engine and frame, and the two smaller connections on it are clean and tight.

The two connections on the back of the alternator, one goes directly to engine computer, the other picks up system voltage. theone going to the engine computer is basically PWM grounding the Field connection, to maintain the voltage.

My voltage regulation on my '89 was a YoYo of 13.7 to 14.9v with unexplained spikes occurring for no particular reason I could ever determine.

I got so irritated as the engine computer Voltage regulator Insanity I added an modified external regulator so I could choose the voltage setpoints manually

. In order to do so You need to add a 50+ watt 10 Ohm resistor between the two wires which attach to the alternator now to trick the engine computer into thinking it is still connected to the alternator.If you do not add the resistor the check engine light will come on and certain parameters of running the engine will go 'open loop' and power and MPG will suffer.

Consider the possibility that the engine computer's voltage regulator is just doing its insanity thing, and that insane is normal for it.

if the voltmeter is a new addition then i'd say ignorance is bliss, and carry on.