voltage leak/ alternator

[robb4100]

Hi Folks,

I am chasing down a voltage leak.

S1/S2 1965: negative earth, alternator; fuse box replacing the old voltage regulator.

If I disconnect the negative battery feed and then measure the voltage from the negative feed to the negative battery post I read 12+ volts. There is no measured current running through the system.

As I was checking this out I disconnected the alternator from the system and the voltage from the negative lead to the battery post drop to 0.

I measured the voltage from the alternator lead to the alternator post and it reads 12+ volts.

Is this normal? If so why is the alternator circuit always closed?

Thanks-

Robb

[prloz]

Hi Robb,
This is normal. The output rectifier stack in the alternator is permanently connected to the battery, ideally through a high current fusible link. What you are reading is the very low reverse leakage current through the rectifier stack, which can be ignored.
Regards,
Peter.

[CBUEB1771]

Hi Robb,
This is normal. The output rectifier stack in the alternator is permanently connected to the battery, ideally through a high current fusible link. What you are reading is the very low reverse leakage current through the rectifier stack, which can be ignored.
Regards,
Peter.

All is normal unless a diode in the rectifier bridge has shorted which can cause the battery to drain when everything is shut off. Robb, tell us just what "voltage leak" you are chasing down. If your battery is draining with everything shut off you might have a duff rectifier.

[robb4100]

I love when a problem goes away and then comes back.

Once again my battery goes from 13 volts to 6 volts overnight. I ran a DC ammeter in the system and I am pulling 2+ amps with everything shut down. I did some checking and the heavy wire from the alternator is pulling 2+ amps.

I disconnected the wire and expect that the leak should be stopped. I will know in the AM.

If this is a bad rectifier as suggested earlier-what is the remedy.

robb
Dumb current owner

[robb4100]

Thanks Guys

The problem was a bad voltage regulator- been replaced and am good to go