Alternator Voltage Spikes to 18V

[1967Sat]

First time posting, but have visited many times before... Anyway, I have a 1967 Satellite that I have updated/added to the electrical system. Late model wiring harness with the connections for electronic voltage regulator and ignition system. I also installed the front accessory mounts for serpentine system, using the 1992 Dakota 90 Amp alternator with the early regulator. Both alternator and regulator are new... Previous alt showed a bad diode when tested on car. For ignition, MSD ready to run distributor, and running the FiTech fuel system. Now, even before installing the FiTech, I have been getting voltage spikes up to 18V as rpm goes up. Obviously, not good for components running that high of voltage. To try to alleviate to problem, I have run a 10 ga wire from the alternator to a isolated terminal that I have the battery hooked to for accessories not normally run on early Mopars, like an electric fan, fuel pump, etc... Also did bypass on ammeter to prevent that from burning out. All grounds are good, little to no ohms. Also note, battery is in the trunk, since P/S pump won't fit with battery up front (serpentine system)… I have seen a post on a Dodge Ram (early year) with the Cummins, but not so sure this is a fix that will work on the Satellite, but if anyone has done it on their A/B/C/E body and it fixed that problem, let me know with a proper wiring diagram for the relay. Thank you.

 

[dvw]

The regulator and alternator case need to see good ground. If not it will over charge. If the green field wire from the alternator is grounded or rubbing ground it will over charge.
Doug

 

[Nacho-RT74]

Once on same deal MY problem was the alternator being shorted to ground via the rotor. One of the cooling vanes was in friction when spining with one of the stator leads to diodes bank.

Since you bypassed the ammeter we can't know if could be the same. My sympthoms were:
at iddle: heavy discharge reading but 16-19 volts at batt
revving up: charge reading ( barelly passing the center reading ) and 24 volts at batt.
disconecting batt engine stalled.

It took me about around 2 hours to find what it was the problem. WASN'T EASY.

 

[1967Sat]

The regulator and alternator case need to see good ground. If not it will over charge. If the green field wire from the alternator is grounded or rubbing ground it will over charge.
Doug

I check all grounds, and even ran a 4 ga cable from the alternator to the battery, still the same problem. I'm going to pull the alternator and have it tested. If it is that, then I will be beating O'Rielly's for a warranty... Thank you.

 

[Dipstick]

One of the alternator fields has an intermittent ground or the field ground wire has an intermittent short to ground. Might not show up on a test bench.

 

[1967Sat]

The regulator and alternator case need to see good ground. If not it will over charge. If the green field wire from the alternator is grounded or rubbing ground it will over charge.
Doug

Found the problem... Was the new voltage regulator. Had the alternator tested off the engine, and it tested out good. So, I reinstalled the old regulator, and no more voltage spike above 14.8.