Charging system gremlin

-
B

Bobacuda

Well-Known Member
Joined
Dec 1, 2017
Messages
1,473
Reaction score
3,695
Location
Texas
When the ‘67 Barracuda got hot and puked rusty coolant water durning the 4th of July parade, the crap got inside the alternator, and apparently wiped it out.

I watched “how to test the alternator” online, then I tried it on my alternator - and it was not putting out a charge to the battery. Pulled the alternator and it is missing a diode…(see photo).

So, I installed old alternator that I had on a shelf (unknown condition), and it did not charge either. New one ordered. Hope that’s it.

IMG_0065.jpeg
 
I can not tell from the photo, but that might be an early 70/ later in other words isolated field. On any alternator, whether grounded field or isolated field (70/later) you need to determine if the field is continuous, if one end is grounded if you are using a 69/ early regulator, if it is incorrectly grounded if you are using a 70 / later regulator

A quick way is to jumper power to the field terminal and in somewhat subdued light, see if you can see a small spark. Better is to hook your meter in series with the high amperage scale, and see if it draws current.

Be careful that it is not just plain shorted, as the field/ ignition/ regulator circuit is not fused

You also must be careful of rebuilds. Often guys get a 70/ later configuration when they wanted the early type, but sometimes the rebuilder grounded one field whether you wanted that or not, and WORSE, sometimes one field terminal is grounded and the rebuilder LEFT THE FLAG TERMINAL in place. This means that you can mistakenly get the VR wire (pre 70) mistakenly on the grounded terminal, or 70/ later, might by chance get the field power wire connected to the grounded terminal.

This is a simple problem, but you must check it out
 
I ordered an AC-Delco rebuilt alternator on Amazon. Says it is for my ‘67. This is the back.
Anything to be concerned with?
1722300849456.png
 
Regulator was new when I put the car back together. When I bought the car, it did not have one and the wiring was very sketchy. I replaced all of the wiring with M&H wiring.

To the best of my limited knowledge, the regulator is OK. If the new alternator works, but still no charge, that is the next thing to look at.
 
These are an incredibly simple system. The VR MUST be grounded. The IGN terminal of the VR receives 12V from the "run" circuit, and does two jobs--it powers the VR/ field circuit, and also is the voltage sense. The VR when the battery is low, sends field power on green to the flag terminal on the alternator, and the more current, the higher the alternator output. I would check that you have continuity from the one flag terminal of the alternator to ground. If it will not charge, rig a voltmeter on the battery, and with the engine running "fast idle" take a jumper wire, disconnect the green wire at the alternator , and jumper 12V to the alternator field terminal. This should cause full output.

If that works, but it won't charge with the VR and wiring all connected, it might be something in the wiring, or might just be bad VR. To be sure, disconnect the VR wiring, and jumper the two wires temporarily together. Start and run and it should charge, actually overcharge. If that works, and you are certain the VR has a good ground, replace the VR

You can easily burn up a VR by a field short to ground, so use reasonable care
 
Both alts pictured have 5 diodes [ that I can see ]. I do not think one is missing. I would check the brushes & slip rings. Could have corrosion &/or making a bad connection.
 
The new alt charges, but it’s insufficient. Like a 0.25V increase. With the old alternators, the ammeter showed discharge at idle, more discharge with headlights. Now with the new alt, the ammeter sits dead center at idle. However, turn on the headlights and it goes to discharge. I have ordered a new VR.
 
Last edited:
Time to show my ignorance. When I bought the 67 Barracuda, it did not run and there was a number of sketchy and incomplete things. The alt was not wired up with the wiring harness. No VR. I am waiting on a new VR to replace one that does not appear to be working.

Meanwhile, the photo below shows the back of the new alt. The wiring harness connects to the bayonet (wire to VR). The alt does not have a second bayonet (that would need to be grounded), but you can see the screw attached to to something there.

Do I need to make a ground wire and attach that to ground?

Like I said, time to show my ignorance
IMG_0112.jpeg
 
I've had my share of bad electrical joo joo, that's due to my pi$$ poor diagnostic skills. When **** comes up and it always seems to lol, I refer to the FABO witch doctors to figger the voodoo out. That being said I did "upgrade" to the 70+ style charging system. Different alt(squareback) and different style voltage regulator. Both apparently are more reliable/durable and available. Might be something to look into?
@67Dart273 @Mattax may chime in.
Bobacuda said:
Time to show my ignorance. When I bought the 67 Barracuda, it did not run and there was a number of sketchy and incomplete things. The alt was not wired up with the wiring harness. No VR. I am waiting on a new VR to replace one that does not appear to be working.

Meanwhile, the photo below shows the back of the new alt. The wiring harness connects to the bayonet (wire to VR). The alt does not have a second bayonet (that would need to be grounded), but you can see the screw attached to to something there.

Do I need to make a ground wire and attach that to ground?

Like I said, time to show my ignorance View attachment 1716283899
Click to expand...
 
Bobacuda said:
Time to show my ignorance. When I bought the 67 Barracuda, it did not run and there was a number of sketchy and incomplete things. The alt was not wired up with the wiring harness. No VR. I am waiting on a new VR to replace one that does not appear to be working.

Meanwhile, the photo below shows the back of the new alt. The wiring harness connects to the bayonet (wire to VR). The alt does not have a second bayonet (that would need to be grounded), but you can see the screw attached to to something there.

Do I need to make a ground wire and attach that to ground?

Like I said, time to show my ignorance View attachment 1716283899
Click to expand...
You need to check it with a meter, plain and simple. It does appear to be grounded, as the slot opposite it should be for an isolated brush.

This is because the rebuilders have played games for years. They sell newer versions for old and often misconfigure the brush setup, whether for grounded or isolated field.
 
Eureka! Old alt tested bad, replaced it with one that I really didn’t test - system did not charge.

Put a new rebuilt AC-Delco alt on, it tested fine, but no charging. Regulator tested bad. Replaced it and I now have a functional charging system.

Pulled the cover on the bad regulator. If you squint real good you can see the burned wire (non insulated and gray). I guess the hot, rust filled water that did the alternator in killed the regulator as well
IMG_0149.jpeg
IMG_0148.jpeg
 
Last edited:
Bewy said:
Both alts pictured have 5 diodes [ that I can see ]. I do not think one is missing. I would check the brushes & slip rings. Could have corrosion &/or making a bad connection.
Click to expand...
:wtf:
 
Bobacuda said:
Eureka! Old alt tested bad, replaced it with one that I really didn’t test - system did not charge.

Put a new rebuilt AC-Delco alt on, it tested fine, but no charging. Regulator tested bad. Replaced it and I now have a functional charging system.

Pulled the cover on the bad regulator. If you squint real good you can see the burned wire (non insulated and gray). I guess the hot, rust filled water that did the alternator in killed the regulator as well View attachment 1716285709View attachment 1716285710
Click to expand...
Awesome!! To answer Your question, the 2nd brush has no insulator on the holder, so it is grounded to the case.
 
You must log in or register to reply here.
-

Back
Top