Alternator Bad?

[Beep69]

69 RR 383. At idle im at around 12.2. When I up the RPM I go to 12.4. I changed out the voltage regulator and no change. Brought the RR to Autozone and they tested the alternator. They said the internal voltage regulator in the alternator failed and I need a new alternator. Do 1969 roadrunner singe wire alternators have an internal voltage regulator or did the autozone employee mistaking. Maybe he meant the external voltage regulator on the firewall? Need help. Thanks in advance

 

[dadsbee]

There is no voltage regulator inside a stock alternator.

 

[Beep69]

That's what I thought. I wonder if the machine read that my external voltage regulator was bad. How to I test the external voltage regulator.

 

[LowBikeMike]

Do you have an original alternator or an aftermarket one wire unit? How many wires are attached at your alt? Pictures?

 

[Chuck Marshall]

Where are you taking the voltage reading off of? The positive battery feed? If the engine is not running and you read 12.4 or more, you are just reading battery voltage when the engine is running and not charging voltage which means the alternator is not charging. You probably have a bad alternator. I would not condemn the voltage regulator, they are made to regulate the voltage to not exceed Around 14.5 volts. Just my thoughts

 

[Beep69]

Here are some photos. I think it's the original style alternator but please let me know. I got voltage off the battery. pos and neg terminals while running.

 

[Chuck Marshall]

what is your battery voltage not running?

 

[Beep69]

what is your battery voltage not running?

12.2 to 12.3

 

[Chuck Marshall]

Ok so based on that the alternator is is only making .2 to .5 volts. Running at idle it should be 13.5 to 14.5 volts. You might want to take the alternator to a alternator rebuild shop to be tested and evaluated not an Auto Parts store

 

[Beep69]

Ok so based on that the alternator is is only making .2 to .5 volts. Running at idle it should be 13.5 to 14.5 volts. You might want to take the alternator to a alternator rebuild shop to be tested and evaluated not an Auto Parts store

ok thanks

 

[Chuck Marshall]

You can put the bolt meter directly on the battery post on the back of the alternator and the negative on the battery negative and start it to see what the voltage is. If it’s still 12.4 or so then you’ll now it the alternator

 

[Chuck Marshall]

Volt not bolt sorry mis spell

 

[Billccm]

I've been down the same route. My alternator failed the rectifier test at O'Reilly's.
Currently having this shop rebuild it for $90.
Home - Luna Industries, Inc
I figured it's got to be better than the $79 O'Reilly's Mexico rebuilt.

 

[dadsbee]

Pull the green wire off the alternator. Use a short jumper wire from the output lug and touch it to the field lug you just took the green wire off of. Does the voltage go up, as this should make it go full charge.

 

[Nacho-RT74]

I think it could be one Diode or stator winding coil is gone.

 

[RJRENTON]

Pull the green wire off the alternator. Use a short jumper wire from the output lug and touch it to the field lug you just took the green wire off of. Does the voltage go up, as this should make it go full charge.

By doing this test, you prove that the alternator can produce full output. iF, the alternator does NOT produce full or maximum output, the likely cause is an open diode. The alternator is a full wave three phase bridge rectifier design.....3 positive diodes and 3 negative diodes which rectify or change the generated AC current and voltage to DC to charge the battery and operate the vehicle. IF any of the diodes (either positive or negative) fail or open, the capacity of the alternator is reduced by hslf or 50% of the origional design output. Diodes must be checked ndividually for resistance to determine which diode is open....diodes cannot be tested as a group but only one at a time......
BOB RENTON