[hotrodcommuter]

First, my system has worked fine for the last year.
My 65 impala runs on a 3 wire system, a large Delco alternator, the resistor wire goes back to the original idiot light in the dash.
Suddenly, it quit charging today, when I turn off my battery kill switch, the car dies, so there is No charge coming from the alternator.
I used a light tester to test the wires running to the idiot, dash light, and both were hot with the car running, but no charging. The light itself never lights up, and never has.

Any ideas?

[EOD Guy]

is the bulb burnt out? Leave the alt connector in place, run a jumper from the pos post of the batt and wedge it into terminal 2 on the alt connector see if it's charging, use a multimeter at the battery posts...... NOT by unhooking the battery. Unhooking the battery and allowing the alt to run the car allows unstable and damaging voltage spikes to enter your system and is very bad for electronics, the battery acts as a buffer. If the voltage doesn't read around 14 ish volts, with the car running, at the battery post your alt is fried.

[hotrodcommuter]

thanks for the advice; which one is terminal '2', the large wire or small? the bulb has NEVER worked, so I assume it's a bad bulb, does that matter?

[hotrodcommuter]

also, if number two is NOT the one that goes to the bulb, then, yes, that goes right back to the batter currently.

[T-bucket23]

If you unplug the connector from the alternator and turn the key on you should have battery voltage on pin 2 and something less, like 8 or 9 volts on terminal 1. If not then you need to find out why.

It is actually terminal 1 that is attached to the idiot light and the light provides resistance to drop the voltage.

A quick test of the alternator can be performed buy running a jumper wire from the large battery stud to the #1 terminal. This will turn the alternator on. If the voltage is low with this jumper in place then the alternator is bad. If the charging voltage go up to 14 or so then you have a wiring issue. The #2 terminal is just a voltage sense wire. It should be connected somewhere near the fuse panel.

[hotrodcommuter]

I just had autozone check the alternator, and they said it's bad, but sometimes they're machine is wrong.

I don't have a volt tester, but I have a light tester, and the the wire to the dash light lights up, and the ignition wire to that light lights up. But there is no charge at all coming out of the alternator.

[EOD Guy]

T is correct, it is terminal 1 for the exciter wire or idiot light. Sorry fingers get fat sometimes.

The idiot light will only light when you 1st turn on the key, alt not turning or if the alt quits putting out juice.

Basicly..... when you 1st turn on the key, there is power provided to the dash side of the idiot light (before the car starts) and the alt gounds itself internally providing the ground on the alt side of the idiot light and the light should light. After the car starts, the alt is no longer internally grounded and terminal 1 starts to provide power to the alt side of the idiot light...... since the idiot light no longer has a path to ground the light goes out. If the alt has an internal fault.... it provides the grouund etc........

You don't have to have an idiot light, or a diode just a switched 12volt provided to terminal 1..... BUT your car must be wired for that or a condition called "run on" may occur..... basicly when you turn the car off, the alt will still provide 12v to the ing sytem etc.....and the car won't shut off.

[EOD Guy]

As far as which terminal is which, look at the "last photo" by my avatar

[hotrodcommuter]

it was the internal voltage regulator,,,go figure!

[EOD Guy]

Good to see you got it sorted out