duster sporadic starting/not charging?

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73 Plymouth Duster

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So i couldn't really find a thread that matched my problems. 73 Duster, new ballast resistor new voltage regulator, new (2 years ago stater relay), new ignition switch and I just had o'reilly bench test my alternator and it is fine. So here are the symptoms

1st symptom:
Car normally starts right up but occasionally when you'd turn the key the starter would start to engage and then nothing once I pass about the halfway point in the key. Its like it will try to start on the run circuit and not the start circuit of the switch. But this can be fixed by backing the key back off or turning it off and on again normally the starter will engage at all angles of the key turn. After all that though it will sometimes sit there and crank for 10 sec before it will start like there is no spark for a little while? (but the tach still jumps around reading little impulses while I'm cranking). I've noted this problem seems to occur when the battery is way low on juice, read below.

2nd symptom:
The car battery would show like 12.6 volts while running and after driving it for 30min it could barely start/ someone had to jump me since the battery read like 11 something volts, so it wasn't charging. I had the alternator bench tested, it was fine and I just replaced the voltage regulator yesterday which seemed to fix it. When I try and start after driving for a while it fires right up but has started doing the funky key thing where it wont engage past halfway sometimes. AND it still only reads 12.6 volts while its running...so it isn't charging? or it is a little? Because Ive driven it for more than an hour and the battery is still fully charged...but will only read 12.6 while the car is running? shouldn't it read more? My ammeter inside also never shows a charge.

So any ideas on what my problem could be? ive checked wire connections and ohm tested between them, all checks fine.

Thanks in advance for the help!
 
There is something wrong with the sw or its installation.
If you fix the switch issue, I think the rest will sort itself out. On my 73 the swedging let go between the lock-cylinder and the chrome plated outer twist-to-start handle. Lots of problems. Its fairly clear that the alt is not receiving a signal from the ig sw.It cound be as simple as a failing connection at the "N" port, or the VR, or the VR ground, or some combination. But I think its in the switch or its install.
Make sure the connections on the back of the ammeter are tight.
 
What voltmeter are you using to look at the voltage? An aftermarket installed one in the dash area? If so, where is it connected? To get an accurate reading, you need to have it connected close to the battery; the large lug on the starter really is a good spot. If you connect it further towards the voltage regulator/ignition wiring, the voltage drops will give you an inaccurate reading.

Using a test voltmeter, you should read between 13.7 and 14.3 volts across the battery at fast idle and warmed up. Voltage at low idle is not a good indication. Measure at the alternator output to battery - also; is should not be a whole lot higher than at battery +.
 
12.6 when running simply is not charging, or charging so little that it barely "is."

1....Check belt tension

2....Don't believe the parts store bench test

3....Suspect trouble in the alternator output wire

Review the simplified diagram at MAD electrical: (while you are at it, read the article)

amp-ga18.jpg


What you want to do is to check the alternator SYSTEM in several different SECTIONS

1...Field/ regulator / brushes

2...Output "charging line" IE output from alternator through the harness to the battery

Start the car and run at a good fast idle. Check battery voltage. On a normal car it should be anywhere form 13.8--14.2 "warm" and when first starting, might be say, 13.2--15 or so. It should be substantially above 12.6

Note the reading, whatever it is. Now move your meter probe to the alternator output stud. This voltage, assuming "normal" and the battery is charging some because it just got done starting the engine, might be 1/2 volt or nearly 1 volt HIGHER than whatever battery voltage is

If the battery V is low, down around 12.X and this voltage is near that......it's not charging or not charging "much."

If the battery V is 13.X and higher, and this voltage is 1/2-1 volt higher, that is OK

If the battery V is low, and this V is quite high, MORE than 1V above battery, YOU HAVE a bad connection in the path to the battery. Review the diagram. Might be bad connection right at alternator (bad wire terminal) bad at bulkhead (either red or black) or at alternator. VERY rare but has happened is failure of the "welded splice" which is inside the car, under the dash, in the black ammeter wire a few inches from the ammeter
 
Field section. First thing to do is determine if the alternator is capable of outputting full output. It might have one or more bad diodes, bad stator, rotor, or worn brushes. "Rig" a clip / test lead(s).


Remove the GREEN field wire. Clip a lead from that alternator field terminal to ground. Turn the key to "run". Measure voltage at the OTHER field terminal, blue. It should be close to battery voltage

IF SO start the car, monitor battery voltage, and bring up RPM. Voltage should come right up, ammeter should show substantial charge, and V should climb above 13.5 and beyond. Turn on headlights, heater....With engine at fast idle, V should remain at least 13.5. or above. Don't rev engine and don't allow V to shoot past 15 by much.

If the above checks out OK, hook alternator wiring up "normal." Disconnect blue wire this time and ground that alternator terminal. Do NOT ground the blue wire, let it "hang."

Remove VR harness connector. Use screws (10-32? etc) to "make" terminals and jumper across the two connections in the VR harness connector. Repeat the above test. Should get same results.

===========================================

If the above tests show OK, scrape the VR clean and remount with star lock washers. The VR MUST be grounded. Inspect the VR connector and pins for looseness, corrosion. If this looks OK and it still won't charge, replace the VR
 
67Dart273 said:
Field section. First thing to do is determine if the alternator is capable of outputting full output. It might have one or more bad diodes, bad stator, rotor, or worn brushes. "Rig" a clip / test lead(s).


Remove the GREEN field wire. Clip a lead from that alternator field terminal to ground. Turn the key to "run". Measure voltage at the OTHER field terminal, blue. It should be close to battery voltage

IF SO start the car, monitor battery voltage, and bring up RPM. Voltage should come right up, ammeter should show substantial charge, and V should climb above 13.5 and beyond. Turn on headlights, heater....With engine at fast idle, V should remain at least 13.5. or above. Don't rev engine and don't allow V to shoot past 15 by much.

If the above checks out OK, hook alternator wiring up "normal." Disconnect blue wire this time and ground that alternator terminal. Do NOT ground the blue wire, let it "hang."

Remove VR harness connector. Use screws (10-32? etc) to "make" terminals and jumper across the two connections in the VR harness connector. Repeat the above test. Should get same results.

===========================================

If the above tests show OK, scrape the VR clean and remount with star lock washers. The VR MUST be grounded. Inspect the VR connector and pins for looseness, corrosion. If this looks OK and it still won't charge, replace the VR
Click to expand...
Thanks! Just got the Duster legal and drove to a friend's memorial service. Had starting issues 2x ( jumped it), got her home, looks like the green wire is toast.
 
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