Randomly over charges, volt gauge pegs st 18 volts, check gauge light comes on. Have changed pcm $330, still the same. Have tried to check voltage when it happens, by time I get hood open and multimeter connected gauge goes back to normal. No codes set. At a loss.

 

Do you have other signs of the voltage going high such as the lights getting brighter?

It could be a gauge/cluster malfunction.

Verify all grounds/connections to the battery and alternator are clean and tight.

You don't need to open the hood. Wire up a lighter plug to your meter and keep it plugged in.

 

Yes, dash ligjts would flicker slightly, eventually transmission wouldn't shift out of low. When changing pcm the connector furthest from radiator had thick brown fluid in it, cleaned with electronic cleaner before installing new. Everything worked fine for 3 days then gauge started pegging at 18v with check gauges light again, shifted fine, only drove about 50 miles total before symptoms started again. Did not drive any more due to going out of town.

 

Don't know if this matters, 2000 Dakota 4x4, quad cab, 4.7, auto, 228000 mileage.

 

Your power steering pressure switch is leaking. That's the source of the fluid. It migrates inside the insulation of the wires to the connector.

Try cleaning the connectors again - and replace the power steering pressure switch.

 

Replaced psps about 2 months ago as it was leaking for quite awhile, got tired of adding fluid, it's on opposite side of engine. The voltage spike didn't start till after it was changed for about a month, you would think it would have had voltage spike before and fluid would have dried by now. Is it possible to put a regulator between alt and pcm or wherever?

 

Anything is possible but you'd likely have a CEL for the alternator.

Try cleaning the connectors thoroughly.

The oil in the connector is a common problem and it takes forever for it to clear up.

 

CEL? What is that?

 

I'm wondering about the alternator. Possible diode going bad would cause voltage spike as well as flickering of any kind. AC voltage will do all kinds of crazy stuff. Just a thought.

 

CEL check engine light