voltage fluctuation HELP!

[69dodgedart360]

hey everybody, i have a problem that i cant seem to figure out. when i am cruising (anything over 1500rpm) the voltage gauge reads its putting out 15volts, but as soon as i come to a stop, it immediately drops to 13v which is fine but the problem is sometimes (because this is an intermittent problem) stoplight to stoplight, it will drop real low to 12-11volts for some reason and i am forced to throw it in neutral and give it gas or manually shift the car so it wont die out because it starts to idle really rough. It also makes the car hard to start after i park it while i am having these problems. This has been going on for a long time, I have changed two alternators, three voltage regulators, a ballast resistor, a coil, and checked the grounds. everything that i think i should check i have and the most frustrating thing is that somedays its ok but other days it does this to me.
HELP!
P.S. this has happend with my old factory guage set-up and new set-up. if it helps i just ditched all of the factory guages and put in electrical auto meter sport comp 2's

 

[player1up]

The only way to diagnose intermittent electrical problems is to spend a lot of quality time with a volt meter and your wiring. Do your research first and forget everything that you have tested up to this point and start over.(test everything again)
I'd verify what your volt gauge is telling you by check voltages at battery, alternator, voltage regulator, fuse box. Then move further out in the circuits like lamps and indicators. From there you should be able to see where the voltage drop is coming from. Also write down everything from outside temp to how long the car has been running, what accessories are being used etc.
Even if its working, check it, then you can compare working with non working values of the same tests.

If you think its heat related you can use a heat gun or hair dryer to test and alternately compressed air from a can (turned upside down) to cool things
Try not to change too many things at once to avoid the "now which change fixed it?" situation.
I'm assuming that if you've changed the gauges that you have a pretty good understanding of wiring and a wiring diagram of the car. Go through the diagram so when you are doing the tests you can picture what gets power from where.
If plausible isolate the charging circuit with new wires ( run a few new temporary wires to the volt meter, regulator and alt) and pull all unnecessary fuses.

That's what I would do...I know REALLY time consuming but it sure beats selling the car because you can't figure it out only to have the buyer call you up and say it was just a loose wire....

 

[KitCarlson]

Bulkhead connector, and battery are good places to check. Have a load test done on battery. It could be a intermittent bad cell, dropping the voltage by 2 volts. Bulkhead connector may be corroded or loose.