Not charging with headlights on

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trebor75

trebor75

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My car is a 1970 Duster with a 1965 273 engine. I have the Pertronix Flame Thrower Coil and the Ignitor distributer and a bypassed ballast resistor. Everything has worked fine for a year this way.

I noticed while driving home in the dark that my headlights where dim and that my alternator ammeter showed the car was not charging, see picture. I turned the headlights of and it went back up to the middle. Because It was dark I had to have the headlights on so I went straight home. Getting close to home the car started to stutter, I turned headlights of and it stopped.

I have very little knowledge of electrical issues. I re-charged the battery and checked it with a multimeter. With the engine in idle without the headlights on it read 12.20 and while reving it quite hard it never went up to more then 12.27. With headlights on it read 12.02 on idle and did not went up at all while reving.

My friend had an spare alternator (not sure of the condition of it to be true), so I tried that and it was the same.

I’d really appreciate some pointers on how to use the multimeter to look for the issue before buying a new voltage regulator or alternator. Tried to explain best I can in english aswell :)
 

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Were you reading the voltage at the battery, or at the back of the alternator?

I'd be curious as to what you are getting at the back of the alternator. The factory charging system on these cars is pretty finicky. If you are still getting less than 13.8V (it should really be more than that) at the back of the alternator, I would at first check to make sure the regulator has a good ground and that all the charge wires and connections are undamaged.

I had many issues over the years with the charging system on my own 70 Duster. I eventually got tired of it and swapped it to a Delco 12SI alternator and have never looked back. The thing works fantastic. Now, in order to do that, you'd have to do a lot of supporting mods...the MAD electrical bypass, big charging wire, and some custom brackets and a small amount of wiring.
 
goldduster318 said:
Were you reading the voltage at the battery, or at the back of the alternator?

I'd be curious as to what you are getting at the back of the alternator. The factory charging system on these cars is pretty finicky. If you are still getting less than 13.8V (it should really be more than that) at the back of the alternator, I would at first check to make sure the regulator has a good ground and that all the charge wires and connections are undamaged.

I had many issues over the years with the charging system on my own 70 Duster. I eventually got tired of it and swapped it to a Delco 12SI alternator and have never looked back. The thing works fantastic. Now, in order to do that, you'd have to do a lot of supporting mods...the MAD electrical bypass, big charging wire, and some custom brackets and a small amount of wiring.
Click to expand...

I read it at the battery. My reading at the alternator, which i did by putting the multimeter positive on the big positive stud at the alternator and then ground to the enginge gave me less than at the battery. Dropped under 11 With headlights on. I could not rev though casue it was only me there at the time.
 
May i ad i never had This problem before and i had This car since 2005.
 
67Dart273 will chime in and give you some tips. He's a electrical wizz! tmm
 
I'll let someone else guide you through diagnosis. My best guess is a diode in the alternator has failed. These step up the alts output as required when they work properly.
 
I found these two tests on the forum and did them. I do have the same 12v on both tests as the battery:

"To troubleshoot, get a meter or lamp, first clamp the meter/ lamp to ground (battery negative) and probe the big stud on the alternator. Make sure it's hot, has 12V same as battery.

Next, turn on key to "run", unhook GREEN field wire from alternator, and probe the EXPOSED TERMINAL on the alternator. It should be 12V same as battery"
 
The strategy of a problem like this in general is

1--First define the problem. Your voltage readings have done that--the system is not charging, or very very little.

2--Determine the general area of the problem. That is, bad alternator, bad regulator, a wiring problem or bad connection

First, let's be sure what you have. Since you have an older engine, someone MAY have used the old alternator, and we need to determine if you have the 69/ earlier system, or the 70/ later system.

The 69/ earlier system has just one "push on" small field wire connection on the alternator

The 70/ later system has two "push on" connectors, that is, two field connections.

The 69/ earlier regulator has one screw terminal and one push on terminal

The 70/ later regulator has a rubber two terminal connector.

I'm going to assume that you have a proper 70/ later system, post back if that is not the case.

First, a quick couple of checks:

As previously mentioned, the regulator may have lost ground. Dismount the regulator, make sure the bolts were tight (not stripped) and clean and scrape around the bolt holes on the firewall and regulator. Use star lock washers. If there is any question, add a no 10 or larger ground from one regulator mount bolt to a certain ground point. The regulator MUST be grounded "same as" battery voltage

Next, Find the green field wire and disconnect it from the alternator. Take a clip lead and connect to the field terminal on the alternator you just now exposed. With the key in "run" hook a voltmeter to the OTHER (blue) field connector without disconnecting the wire, that is, "back probe" the connector. You should read "same as" battery voltage

If possible, with the engine shaded from the sun, connect the clip lead to ground. You should have one end to ground, the other hooked to the alternator field where you disconnected the green wire. Connect / disconnect this and watch for a small spark. Also check your meter. The voltage may drop a SMALL amount when you ground the clip, but not much.

This shows that the field circuit is getting power, and that the brushes and field are conducting current.

Now start the engine and watch the ammeter. When you bring up RPM the ammeter should show a hard charge, hard to the right. Turning on lights, heater, and with the engine at fast idle, should keep the needle to right of center at least some what.

If this does not happen,

with the engine running fast, Check battery voltage and voltage at the large alternator stud, with your clip lead stilll grounded. If the voltage at both points is close to the same, below 13, it is not charging

If voltage at the alternator is quite high, much above 14, but 12.5 or less at the battery, then you have a wiring problem in the charging circuit.

If these tests show no charge, replace the alternator


Post back with results.
 
67Dart273 said:
The strategy of a problem like this in general is

1--First define the problem. Your voltage readings have done that--the system is not charging, or very very little.

2--Determine the general area of the problem. That is, bad alternator, bad regulator, a wiring problem or bad connection

First, let's be sure what you have. Since you have an older engine, someone MAY have used the old alternator, and we need to determine if you have the 69/ earlier system, or the 70/ later system.

The 69/ earlier system has just one "push on" small field wire connection on the alternator

The 70/ later system has two "push on" connectors, that is, two field connections.

The 69/ earlier regulator has one screw terminal and one push on terminal

The 70/ later regulator has a rubber two terminal connector.

I'm going to assume that you have a proper 70/ later system, post back if that is not the case.

First, a quick couple of checks:

As previously mentioned, the regulator may have lost ground. Dismount the regulator, make sure the bolts were tight (not stripped) and clean and scrape around the bolt holes on the firewall and regulator. Use star lock washers. If there is any question, add a no 10 or larger ground from one regulator mount bolt to a certain ground point. The regulator MUST be grounded "same as" battery voltage

Next, Find the green field wire and disconnect it from the alternator. Take a clip lead and connect to the field terminal on the alternator you just now exposed. With the key in "run" hook a voltmeter to the OTHER (blue) field connector without disconnecting the wire, that is, "back probe" the connector. You should read "same as" battery voltage

If possible, with the engine shaded from the sun, connect the clip lead to ground. You should have one end to ground, the other hooked to the alternator field where you disconnected the green wire. Connect / disconnect this and watch for a small spark. Also check your meter. The voltage may drop a SMALL amount when you ground the clip, but not much.

This shows that the field circuit is getting power, and that the brushes and field are conducting current.

Now start the engine and watch the ammeter. When you bring up RPM the ammeter should show a hard charge, hard to the right. Turning on lights, heater, and with the engine at fast idle, should keep the needle to right of center at least some what.

If this does not happen,

with the engine running fast, Check battery voltage and voltage at the large alternator stud, with your clip lead stilll grounded. If the voltage at both points is close to the same, below 13, it is not charging

If voltage at the alternator is quite high, much above 14, but 12.5 or less at the battery, then you have a wiring problem in the charging circuit.

If these tests show no charge, replace the alternator


Post back with results.
Click to expand...

Thanks. I'll see if I can get this done tonight or tomorrow morning and post back. I do have the 70's system and here is a pick of my alternator. The wire that looks a little green is actually more white, so someone probably changed it at some point. I did do a test earlier today where I disconnected the blue wire at the field, and then with the key in run and the voltmeter hooked up to battery positive and the disconnected blue field terminal it read 12v, the same as at the battery.
 

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Your photo triggered a thought. If you replace the alternator, the later design known as a square back is far superior to the older known as a round back. DO NOT under any circumstances allow a parts store to sell you a "round back"

Newer square back on left

mopp_0112_05_z+alternator_and_regulators+replacement_alternator.jpg


The second reason not to accept a roundback is that many rebuilders actually converted the older 69/ earlier grounded brush design to a "newer" isolate brush by hacking the housing and adding a second isolated brush. Do NOT accept one. Below, the "hacked" brush was added at top, at 12 o clock. This one is missing, you can see the hole

128306-500-0.jpg
 
I have a squareback on at the moment. A friend lent me it. Had the same results with that though. But now i have new info. I did everything you wrote and it came out just as you described. With the green field terminal grounded to the enginge it charges and charges more when i rev. Both at the battery and the alternator. So what do i do next?
 
I never went over 15v but i Think i could have easily done that.
By the way, when i read the blue terminal with the wire still connected and the Green one not grounded it wandered slightly and never made it up to battery 12v. At most 11.50. It dropped some when i grounded Green just as you Said. Writing from My phone. Sorry bout spelling!
 
OK the alternator is good, and the blue wire is good, supplying 12 v to the field.

Now, Check wiring at the regulator connector

To do that, you now want to hook the wire back up to the alternator which goes to the regulator. This would normally be green, but I see yours is not.

This diagram might help

The wire I had you unhook is the field wire marked green at the bottom.

Now hook that up and UNhook the blue field wire, on the diagram, goes over to the ballast. Take your clip lead and ground the alternator field terminal you just unhooked.

Now go up to the regulator connector, and devise a way to jumper across the two terminals. This might take two people, you can use machine screws, nails, etc

Repeat the run test, IE the alternator should charge full tilt, more with more RPM

If this happens, make doubly sure the regulator is grounded.

"Work" the regulator connector on off several times and examine it for corrosion. Hook everything back up "normal" and see if it charges.

If not, replace the regulator.

Dual_Field_Alternator_Wiring.jpg
 
Thank you so much for taking time to walk me through this. I am really greatfull for that! Tomorrow i'll bring a friend to help me out with these new tests and will post back the results.

Thanks and have a nice day meanwhile!
 
Yer welcome. Post back to this thread when you get further.
 
Hooked everything up exactly like you wrote and with the same result. It charges full and increase a LOT with rpm. I took the regulator of the firewall, cleaned and sanded every contact area. Put it back. Still wont charge. Juggled the connector with no result. I guess i should get a new regulator now.

I really learnt a LOT from you! Now i know exactly how to help someone in the same position! Thanks!!!
 
I also wanted to add my thanks for the excellent advice. Using the advice above I was able to trace troubleshoot my non-charging, voltage drop problems. Like most things it was a combination of small things that added up. For the first time in a long time I'm able to see my Valiant charging strong. The only thing I can add is take apart all old splices and solder them!

Thank you so much for sharing your expertise. It makes FABO a really special place.
 
You're very welcome. I've always been "low buck" and HATE wasting money on parts ya don't need. You could have gambled "thrown" an alternator and regulator at it, at it might have worked fine. Then again, it might have been a simple wiring problem, and many dollars worth of new parts would have done you no good.
 
I have some charging problem on my Barracuda too, so I am glad this help is here. I will do all these tests and hope to find and correct the fault.
Thank you
 
So, this probably doesn't belong in this thread but considering everything that's been going on with my car, I thought I'd try.

So now I'm getting between 13 and 14.5 at best at the battery and the voltmeter. I took it out for a 30 mile run just to check it out and all was well. When I go to start it today, it will run for a little then sort of starve out. There seems to be plenty of gas in the carburetor and it runs strong at high idle but chokes out when I let it go. This is totally new behavior and I'm wondering if I might have messed something else up? I did change the ballast resistor to make sure.

Any thoughts?
 
mnmopar said:
So, this probably doesn't belong in this thread but considering everything that's been going on with my car, I thought I'd try.

So now I'm getting between 13 and 14.5 at best at the battery and the voltmeter. I took it out for a 30 mile run just to check it out and all was well. When I go to start it today, it will run for a little then sort of starve out. There seems to be plenty of gas in the carburetor and it runs strong at high idle but chokes out when I let it go. This is totally new behavior and I'm wondering if I might have messed something else up? I did change the ballast resistor to make sure.

Any thoughts?
Click to expand...

You probably should start a new thread. Could be a number of things, and any of these old girls should run for hours and hours right off the battery.
 
I did all the tests and that is result:
When green field wire not connected, 12.9 at battery and 12 at black cable on regulator.
With engine running 11.8 at alternator big connector.
I suppose the alternator is not working.
Alternator is a round one labelled as reworked (made in Mexico).
Any advice
 
cadboy,
You didn't list results for all the tests. Don't condemn the alternator until you measure no output (big stud) with 12 V across the field terminals. Most round-back alternators ground one of the field terminals to the case (info above). Even then, the alternator may not be bad, it may just not be getting a good ground to the engine. Insure the case voltage is close to BATT- to check that.

trebor75, before you condemn your Vreg, insure it is getting +12 V supply from the ignition key. That is the voltage it senses and attempts to regulate to ~13.4 V.
 
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