Charging issue!

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Twotone22

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I have 69 dart 225 and while my girlfriend was driving home from L.A. the alt Gauge dropped to below the halfway mark. After checking and testing the battery, starter and alternator at the local parts house we came to the conclusion of a bad voltage regulator. However after further searching I found a GM alternator from a late 70's truck. A 7127 model I believe. The internal on the alternator is not plugged into anything. I cannot find a vr anywhere on the car and the hot from the alternator seems to run directly to the starter relay. The car still runs normal but the gauge is still reading low and the radio won't stay on. I'm now officially lost. Please help with any ideas. I can't bare to leave my baby in the driveway!
 
The voltage regulator is on the drivers side firewall left of the mastercylinder. Get rid of the cheapy gm alt. and fix the real problem. Whatever it may be.
 
the GM alternater has a little part in it called a trio-diode that fails. Its expensive and not too difficult to replace.
 
Twotone, some of what you say does not make sense.

IF THE ALTERNATOR output is actually connected directly to the starter relay, then the factory in - dash AMMETER (it is not an "alt gauge") is not in the circuit.

Or did someone add an aftermarket VOLTMETER?

You need to measure the battery voltage right at the battery with a meter, with the engine running "to simulate low cruise" RPM

Your original regulator should look like this:

a20792a12d51ecd5aaf8a2_m.JPG


To see if the original alternator is OK, take a clip lead and clip the two wires on the regulator together, start the engine, and check with your meter on the battery. Bring up RPM slowly, and the meter (voltage) should start to climb if the alternator and wiring is OK.

(Once again, if the output stud has been hooked to the starter relay, the in-dash ammeter is no longer in the circuit)

If the above is OK, you just need a new regulator.

The GM 7127 would be OK if you want to go through the trouble of adapting it. Not having a connector on the GM "one wire" is NORMAL. If you think it's in good usable shape, it should work fine.
 
The "alt" gauge always read to the right of middle. Now it won't rise above left of middle. I have to assume it's in circuit because with the gauge to the right, the radio worked fine. Now with the needle to the left, the radio stays on only for a few seconds and the headlights will dim if not on the gas.
 
Twotone22 said:
The "alt" gauge always read to the right of middle. Now it won't rise above left of middle. I have to assume it's in circuit because with the gauge to the right, the radio worked fine. Now with the needle to the left, the radio stays on only for a few seconds and the headlights will dim if not on the gas.
Click to expand...

We cannot help you much if you won't give out more info. None of us are mindreaders

It's not an "ALT" gauge. So are we talking about the in dash factory AMMETER or are we talking about an aftermarket VOLTMETER that someone added? Or did someone add an aftermarket AMMETER?

If the alternator stud is jumpered directly to the starter relay large stud there is no way in hell that the factory AMMETER will read correctly. It is effectively bypassed.
 
It is the factory ammeter. Sorry for the confusion. Turns out the line from the alternator is going to a small junction box to the left of the master cylinder but it looks nothing like any of the voltage regulators that I've ever seen.
 
Twotone22 said:
It is the factory ammeter. Sorry for the confusion. Turns out the line from the alternator is going to a small junction box to the left of the master cylinder but it looks nothing like any of the voltage regulators that I've ever seen.
Click to expand...

Hard to say without photos. Does/ did the car ever have a dual battery system? Are you sure you are looking at the alternator output and not the field wire?

The OUTPUT is a large black wire bolted to a stud / nut on the alternator, and should go into the harness up near there. The FIELD lead should be a smaller wire, about no16 and green, and should go to the pictured regulator.

THAT IS probably the regulator, did you see the photos posted above? "Some one" also makes an electronic replacement that is shorter, like this one:

vr706.jpg
 
That's the one I've been looking for. I'll see if I can put up a pic in the morning. It's dark now on the west coast. It is the red wire coming from the "batt" post on the alternator. I goes uninterrupted to this little junction box with several other wires. Thank you everyone for being so helpful so quickly. I really appreciate it.
 
For some reason my computer doesn't want to let me post pics in my reply. But I've replaced the alternator and nothings changed. I've found no voltage regulator. The wire makes 2 stops from the alternator to the bulkhead connector. Then to the starter relay. Still not charging and I'm this close to putting in the shop to let them deal with it.
 
I've got it! When I replaced the old alternator, I did it with a gm 7127 alternator. However, what I needed was a gm 7140 alternator. They look exactly the same but the 7140 is a correct one wire alternator that cometely bypasses both an external and internal voltage regulators. Once I put the 7140 in everything fired right up better than before and with a steady 14 volts.

Thank you again to everyone who tried to help me solve this issue.
 
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