67 383 - On a fully charged NEW battery, at an idle, the alternator show 13V. Under acceleration it shows 17V. Readings at regulator are 14-15V. Where do I start to correct this?

pull all(3) bulkhead connectors off the firewall & clean the terminals & make sure the reg is grounded well would be a good start.

Out of curiosity, why do i check and clean the wiper motor and light connectors? Just trying to learn is only reason I ask

good point, no need, I just have gotten into the habit of doing all (3) at the same time.

Has the alternator been rebuilt recently?

It has not been rebuilt. Do you think the problem lies in the Alternator???

My 318 is from 71 Challenger with original alternator. The high voltage at high RPM's was an internal problem with the diodes.

If grounding the reg doesn't do it, I dont like throwing parts at a car, but do you have another reg off another car you could substitute in for long enough to find out? It's showing 17V at the battery? I think it'd be about to explode

I thought that an overcharge was caused by the regulator. Either it not being grounded good or malfunctioning.

On the single field 67 style alternator voltage is fed from the blue wire thru the regulator to the green wire that connects to the alternator. The regulator senses voltage on the blue wire and sends out a varing signal on the green wire. This controls the field voltage in the alternator thus raising or lowering output. A poor voltage signal on the blue wire (which is fed from the ignition switch),a field shorted to voltage,malfunctioning regulator,poor grounds anywhere in the charging circut loop can all be causes. The most commom are bad regulator,poorly grouned regulator, poor bulkhead conections. I've also seen the bolt on wires at the back of the amp gauge do some weird things. It is possible that the the alternator has an internal short to voltage on the field circut,but it is very unlikely. Hope this helps .
Doug

You are correct sir! It was a grounding problem internal in the alternator. A return trip to the rebuild shop fixed the problem they had created, said it had to do with the diodes. Have not had a problem since. My wiring system is completely new, no bulkheads to deal with and new gauges.

Sometimes people will leave the insulated washer off when they mess with the brushes. That will also cause overcharging. They may blame it on the diodes, but it's possible they just left off a washer.