Thread: Alternator problem

Originally Posted by rar110

I have the standard army type 70 amp Hitachi alternator.

While the ignition is off power is draining from the battery to the alternator. A local auto electrician said I needed a new alternator. I manage to buy a used unit off ebay from a wrecked perentie. The replacement alternator is doing exactly the same thing. I don't believe that coincidently the replacement is doing the same thing.

Any other suggested causes/fixes?

thanks

How have you determined that its draining back through the alternator?

Steve

I got advice from the auto electrician when checking the 1st alternator, and tonight advice from RACQ who put a clamp meter on the power feed from alternator after engine shut down.

I should spend a couple of days disconnecting the alternator. Up to now I've been disconnecting the battery.

Is it possible you have some faulty or burnt out diodes in the alternator hence the leakage out of battery back to alternator.

Originally Posted by neilchoi

Is it possible you have some faulty or burnt out diodes in the alternator hence the leakage out of battery back to alternator.

What's the likelihood of buying one with exactly the same fault as the old one, straight up as soon as it's fitted?

Are you still using the external regulator in your County? That would be common to both alternators and I'm guessing an auto elec who doesn't know County's assumed it was part of the alternator. A regulator contains components such as diodes and capacitors, not the alternator in the case of a County.

Originally Posted by Judo

Are you still using the external regulator in your County? That would be common to both alternators and I'm guessing an auto elec who doesn't know County's assumed it was part of the alternator. A regulator contains components such as diodes and capacitors, not the alternator in the case of a County.

The alternator still has diodes to do the rectification - even with an external regulator. Regulator only controls the field current, and the stator has diodes connecting the windings to a single output stud. If it didn't contain diodes you'd have AC on the output stud.


Steve

It has an internal regulator.

Originally Posted by steveG

The alternator still has diodes to do the rectification - even with an external regulator. Regulator only controls the field current, and the stator has diodes connecting the windings to a single output stud. If it didn't contain diodes you'd have AC on the output stud.


Steve

Actually I thought the regulator also rectified the wave, but I guess I'm wrong. Does the regulator have any direct connection to chassis earth?