Charging problem on 78 Elcamino

I Have A 78 Elcamino and when you turn on the headlights, heater, wipers and then the volts meter goes down into the red. If you Have everything off it charges fine anyone have any ideas. I Have put a new Battery and alternator.

I would start by checking the battery cables and cleaning each fitting on each end of where each cable goes.

Next step would be to bring it to one of the many auto part stores that will check the batter and charging system (more than just the alternator) for you for FREE.

For sure get a free checkout by an auto parts store. It sound like one or two of the three diodes in you diode bridge has gone out. You will still read 13 or so volts, but the current will not be enough to keep charging when there is a demand.

Does this vehicle have a separate voltage regulator?

If so, maybe it needs to be replaced.

What you need to ignore is the dashboard voltmeter. Connect a voltmeter directly across the battery and get a true reading. At a fast idle, the alternator should carry a full electrical load and maintain 13.5 volts at the battery.

I Have checked the volt and it is putting out 13.6 but when you have everything on the volts go down and the lights go dimmer

regulator is in the alternator could it be in the ground with the lights or some other ground