Alternator Not Charging

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Gandy Dancer

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Hello FABO - Does anyone have any recommendations on what items to check if your alternator is not charging. This is a brand new alternator, and the only work related to the alternator that was done prior was the installation of a new starter. Any help is appreciated.
 
What year vehicle? Two wire or 1 wire alternator? I’d check your voltage regulator see if it’s gone bad. Dustin
 
What year vehicle? Two wire or 1 wire alternator? I’d check your voltage regulator see if it’s gone bad. Dustin

WHAT YEAR MAKE AND MODEL and is it the factory setup or have replaced it with something else?
 
Its a 1966 Plymouth Barracuda. I still have the factory setup for the charging system, however I did replace the alternator. I see that it was reccomended to me to check the voltage regulator.
 
I wish you would have come back before "throwing money" at the problem These are fairly easy to troubleshoot I divide the problem into areas

1...The charge output wiring, that is, the circuit path from the alternator, through the firewall connector, the ammeter, back out, and to the battery. There can be a bad connection in that path

2....The field wireing, same deal. We recently had a guy with a broken/ pinched green field wire, which only has a simple job---from the VR to the alternator field terminal

3...The alternator

4...The regulator

SO WHAT DO I DO?

Put a voltmeter on the alternator output stud and ground. You should read "same as battery." "Rig" a jumper/ alligator clip wire from the alternator field terminal to the battery. In subdued lighting, you should see a small spark as you connect/ disconnect. Start the engine and slowly bring up RPM, while watching the voltmeter and ammeter. The voltmeter should rise above 12.whatever, and the ammeter should move to the right. Do not rev up the engine and allow the voltage much past 16V

If the alternator stud voltage does NOT rise, the alternator is bad. If the alternator stud voltage rises, but the battery voltage does not, you have a bad connection in the charge line

If it DOES charge, you are down to field wiring/ regulator

If it does charge..............

Disconnect the two wires at the voltage regulator, green and blue, and jumper them together. Again run the test. If it charges, replace the alternator. If it does not charge you have a wiring problem in the field circuit

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IF you "fix" it and it charges YOU ARE NOT DONE YET. This is because most of these old girls have voltage drop problems which cause OVER charging. To check this..........

Turn the key to "run" with engine stopped. Stab one probe into the top of the battery POS post, and connect the other to the blue VR wire. Leave everything connected "normal." You should read a VERY small voltage the smaller the better. Anything over about .3V (3/10 of one volt) you need to find out why

That circuit path is battery--- starter relay "big stud"---fuse link---through the bulkhead connector---tthrough the ammeter---through the welded splice---to the ignition switch connector---through the switch--back out the switch connector on the dark blue "ignition run" wire---back out the bulkhead connector---and branch off in the engine bay to the ignition and VR. All of the points mentioned above are suspect bad connections

GROUND: A poor ground can cause overcharge. With the engine running fast idle to simulate low to medium cruise, make this test with all loads turned off and again with lights, heater, etc powered on. Stab one meter probe into the top of the battery NEG post. Stab the other into the VR mounting flange. Again, you want the "less the better", zero is perfect
 
67 Dart - I was able to run a jumper from the green field wire to the battery and was able to see the ampmeter charge. When I checked the green wire between the alternator and the voltage regulator I was able to get a positive contact. I thought the problem was the regulator. I swapped it out for the old one which I thought still worked, but I could not get the alternator to send any power through the ampmeter. I am not sure how to test the voltage regulator, so I may just grab a new one.
 
Sounds like it is the VR
That's what I was thinking as well. Less expensive than an alternator, so I will pick one up.

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One other question is do I have to use the old style VR or will the newer ones work as well?
 
One other question is do I have to use the old style VR or will the newer ones work as well?[/QUOTE

Keep the old style regulator. The alternator looks correct. The voltage regulator top phillips screw looks like a sheet metal screw? When installing the new regulator, make sure it is grounded well at the large mounting screws and greased to prevent rust. The smaller screws must not touch any ground.
 
To use the 70/ later you must have an isolated field alternator, which has two field terminals, and add one wire. The added wire must go to switched "ignition run." Most? All? "old style" VRs you buy are now electronic even though they may look similar. What that means is, that IF they are decent quality, they should be a better VR. No mechanical contact points.
 
could not get the alternator to send any power through the ampmeter.
The alternator only sends current through the ammeter when the battery needs recharging.
\/ This is what you should see 95 to 99% of the time.
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If the alternator wasn't supplying any power while the engine was running, then the ammeter would show slight discharge. This is because the ignition coil draws a couple of amps while running.

If this \/ regulator is electro-mechanical internals, you can do a visual check for major problems.
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Take it off, remove the cover and check the condition of the points and fusible links.
Also, although I don't know '66 specifically, based on the photo I'd check the condition of the wire connection to the terminal. Again that could just be the angle of the photo.

If you do need a replacement VR, the factory looking one sold on ebay by FBO seems to have a better rep on FABO than any of the others.
Internally its electronic but it looks and works the same as the electromechanical ones with points.

A multi-meter, even a cheap one, will really help with diagnosis.
We normally want to see the ammeter show some discharge when starting, some recharging after starting, and centered most of the time.
But observing the ammeter in combination with a multimeter set to measure voltage is really helpful when there are doubts.
 
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