Need electrical help 1998 Caravan

My 1998 Dodge Grand Caravan Sport with the 3.3 has an electrical issue. It starts and idles fine, but when when the RPM gets above 2300 the battery light comes on and the LCD dash displays go out. I put a voltage meter on the battery, and it shows 13.8-14.2 volts at idle, but when you rev it the voltage jumps as high as 18 volts! The internet says the voltage regulator is in the PCM. Is my only alternative to replace the PCM or could there be another cause? Could it just be a bad alternator. Is there another test I should perform? Any advice is appreciated!

Not likely the alternator. You could pull it and have it tested.

As you heard, the regulator is built into the PCM. However, there is a solution.

Field Replacement Module

Possibly a ground issue.

Agree

Check and clean the wires under the battery.

don't buy that kit. it seems horribly over priced.
you can buy the regulator and plug for under 20 bucks and run the wiring yourself.

How would a ground issue cause the alternator to overcharge?? What ground would be bad?

Without a ground, the alternator goes to full charge.

Some can and some wont charge at all. I would check the wiring and then unhook the field wire to the PCM to see if it stops charging. On most of them the PCM just ground and ungrounds the field to control output. If it stops charging with the field unhooked then it sounds like the PCM but also make sure the field wire from the alt to the PCM is not grounded as that will make it overcharge. If it still overcharges with the field wire at the alt unhooked then it sounds like an internal alt problem. A grounded brush could also keep it overcharging. And as was said you can wire in an external regulator as I have done that for a few people who did not want to buy and alt. You just run the field ground wire to the ext regulator and also wire 12 volts at key on to the ext regulator to do it that way if its in the PCM. Ron

My fuzzy memory seems to recall those year minivans have a cold solder joint in a ground wire to the instrument panel that is a common problem.

Similar to this:

https://www.allpar.com/model/m/repairs/3G-cluster.html

Marked in red

don't forget to check the wiring harness [everything !] by the battery tray. battery outgassing over the years will attack the insulation, and cause an untold amount of hair pulling, until you find the culprit. [especially the harness parts that are hidden.]
if you have those CLAMP-ON replacement battery terminals, GET RID OF THEM ! those cause MORE problems than you can count !
REPLACE the cables BEFORE you begin to even TRY diagnosing the problem !