Battery, headlights and amp meter

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bigboijc13

bigboijc13

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I am looking to you smart guys for some help here. '73 valiant, battery died the other day, so I replaced the battery and alternator. Since then the battery keeps draining. Had the alternator checked and it is good. I think I have a problem with my lights. When the battery is charged the car starts and runs. The amp meter reads right in the middle. When the lights are turned on, it drops quite a bit. I'm not sure if the lights are what is causing my batteries to drain. Any ideas on where and what to start looking at?
 
BTW, the battery fully dies in about 3 -4 days of driving back and forth to work. 25 miles one way....

Thanks Guys.
 
Without trying to be mean, You didnt mention the obvious thing; the voltage regulator, its wiring or its mandatory ground connection.Nor a word about the charging voltage being higher than the battery rest voltage.
 
If the alternator tested good, then the issue is likley in the voltage regulator or the wiring to it or the alternator. The alternator needs the VR to work properly for the alternator to work in the car. The deflection of the ammeter gauge towards D (discharge) would be normal in this situation. (Note that the ammeter is only ever shows the current flowing into the battery when it is being charged, or when the battery is supplying current to the system for any reason.) Since the alternator is doing nothing, then the battery has to supply all the system operating current and when you turn the headlights on, then the added current for the headlights coming from the battery is showing up on the ammeter as an ammeter deflection towards D.

You can do the following test to verify the alternator and its wiring into the car: Find the small wire that comes from one of the 2 small terminals on the back of the alternator and goes to the VR; this wire is normally dark green. Remove that wire from the alternator, and while the engine is running, ground that wire to chassis or engine block. Look at the ammeter, and it should be reading hard towards the C side. Do this only for long enough to do the check and then take it off immediately; don't leave this hooked up this way; it is even better to have someone ground that terminal on the alternator while you watch the ammeter.

If OK, then:
- check the terminals in the connector to the VR; sometimes these get spread and lose contact. Make sure they are clean.
- remove the VR and clean up the points where the VR case contacts the body so you get a good clean ground; this is critical to proper VR operation. Install clean, non-rusty screws to make sure you get a go ground to the VR case.
- If you can get a voltmeter (a good tool for these cars), then check that the dark blue wires to the alternator and VR have around 12v to them while running.
- If all is good above, then try another VR. Seems like a lot of the junk from the auto stores can be bad out of the box so beware.....
 
Sweet. Thanks for that explanation nm9stetham. I will check this all out when I get an opportunity.

1. Where is the V.R. Located in the engine bay?
2. I am not an electrical expert, but do have a Sperry DM-210A. What settings do I put it on the check this stuff out?
 
I'm sure you've thought of this, but are any lights (glove box, trunk, etc.) staying on?
 
Put the black lead in the COM hole and the red lead in the V hole, and set the range switch for 20 in the black 'V' range with the bar over the V.

- You can check the battery: after ebign charged and removed from the charge for an hour or so ('rested'), a fully charged battery should measure 12.6 to 12.7 volts. (Red lead to battery + and black to battery -.)
- With the car at fast idle and warmed up, you should measure 13.7 to 143 volts acrss the car's battery. If the alternator is good but the VR bad, you will likely measure < 13 volts.
- To check your meter's accuracy, buy a new 9 volt battery; it should measure 9.6 to 9.7 volts.
 
Got it. I went out and checked the battery and it reads 12.4, car off. With it running it reads 12.0. Guess it sounds like the V.R. Huh?

The vr has just 2 wires from it? The blue and the green.
 
Yes on all counts... assuming the test that showed the alternator being good was done right. Your 12.4 volt reading probalby showed that the battery is not fully charged and not that the battery is weak....

You need to clean the VR ground connections and retest. Then if no dice, do the test where you ground the one terminal as I described; that test will verify that the alternator is indeed good and connected in. Since you have a voltmeter, then rather than looking at the ammeter, put the voltmeter across the battery terminals and then ground the terminal described while watching the meter. The battery voltage ought to jump up into the 14-15 volt range. Just do this for a few seconds to verify this.

If you just replacae the VR, and it still does not work then you have to start and go donw the path described anyway. You can throw parts at it or approach it logically; since you have the voltmeter and know how to use it, the latter approach is easy.
 
Thank you so much for the help and explanations.:prayer:

I'll have time to check this out over the Thanksgiving Break. I'll make sure I update you on my progress.
 
So I replaced the voltage regulator, no dice. When I check the terminals on the alternator, car running, one is around 10+ volts, the other one has 1+ volts. Where can I find a good elec diagram of the charging system battery ammeter wiring.

I just don't understand how one day she's fine, the next day there is electrical problems. But that cars though, right?
 
www.mymopar.com has schematics.

We need some more info: There are 3 total wiring terminals on the back of the alternator, right? (It should, for that year.) And you do have the flat pack VR with the 2 terminal rubber plug into it, correct?

Did you measure around 10v at one of the 2 small field terminals on the back of the alternator, and about 1 volt at the other small field terminal on the back of the alternator? If so, then the VR is working and trying to command the alternator to full output. If so, then the alternator is not working... despite the test done before.

GO back to post 4 and do the test described in paragraph 2; the dark green wire should be the one where you measured about 1V (IF I guessed right about where you measured the voltages above) and see if the voltage at the battery jumps from around 12 volts to 14-15 volts when you ground that field terminal on the alternator.
 
So I started the car, pulled the green wire off the back of the alternator, and grounded the alternator, no jump in voltage.

Yes, flat pack vr, 2 terminal rubber plug. Alternator has two field connections, large power post and a separate ground post on it.

So is it the alternator or some wiring?
 
So I figured I'd go look at the fuses right, well I took a picture of the front and the back of the fuse panel.

Looks like the number 2 fuse was drilled out, and the number 1 looks kind of burnt.

Can you tell me what the fuses are suppose to be for?
 

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bigboijc13 said:
So I started the car, pulled the green wire off the back of the alternator, and grounded the alternator, no jump in voltage.

Yes, flat pack vr, 2 terminal rubber plug. Alternator has two field connections, large power post and a separate ground post on it.

So is it the alternator or some wiring?
Click to expand...
OK on the connections to the back of the alternator; that is right for the year.

It would help to be sure if you answered the question of where you measured the 10v and 1v before..... if no answer, we can only guess and may not diagnose the problem right. If measured at the 2 small alternator terminals, and you grounded the terminal that had 1v, then, yeah, it's the alternator.
 
Yes to checking the voltages on the alternator, and grounding the alternator terminal. The lower voltage was the green wire.
 
You should have 12V on that FLD+ exciter closest to battery lug.The alternator should go crazy when you ground the FLD- wire opp of BATT, like spike up to 16 or so. That is the 'volume control' for the alternator lacking any other term. The regulator varies the ground resistance to this terminal based on demand of the system, ie. if the volatage goes under 12, it reduces the resistance on the wire and the alternator outputs a higher charge voltage. So when you turn your lights on, you should see a momentary drop in the Ammeter, then it should bounce back telling you the alternator is now charging at a higher rate. Mopar used to duty cycle the POS input via the points in the voltage regulator but changed the the NEG variable when they went electronic, easier on the transistors. Remove the alt and get it checked. Then check your exciter voltage off the IGN wire.
reminder
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Well, no avail guys. Just swapped out the alternator and the voltage regulator, and same readouts.
12.4 volts at battery, car off.
12.0 volts at battery, car running.
1.4 volts green wire at alternator, car running.
10.0 volts blue wire at alternator, car running.

Not sure what to do or start other than running all new wires for the charging system.

I took the fuse block out, and noticed problems with it. See pictures above.
No. 1 fuse appears to be warped,
No. 2 fuse appetas to have one of the contacts melted off,
No. 3 fuse appears to be warped.
 
Where in Phoenix are you. I am up by Tatum and the 101.
If not outrageously far, I can stop over and give you a hand.

PM me if you wish

I have all the schematics from 67 - 71 I also have a chilton that says it is from 72 - 79

Tomorrow I am booked by after that, no problem
 
Sweet. Definitely will pm you later. At dinner with the family right now. Maybe Saturday. I'm on 12th st and union hills.
 
I can drive it there during the day. Can't drive it at night cause with the lights on it drains the battery too dam fast!
 
Been out working in the field. Well with the readings you are getting on the field terminals, it ought to be working. With the voltage readings on the 2 field terminals, the VR is trying to command the alternator to full output. The only thing I can now think of is that the large main output wire of the alternator is broken/burned out/disconnected somewhere; sorry I did not thnk to have you look at this before.

Measure the voltage at the main stud out of the alternator; even at idle; it ought to be really high in voltage (well above 14v, and could be much higher) if this is the case.

If this is what you find, then trace back the large alternator output wire; it goes through the firewall in the middle set of bulkhead connectors and that would be a good place for it to be burned out, or the contacts corroded and useless. Once inside, it goes to what is called a welded splice, wrapped up in the harness. There are several wires that are pressure welded together at one point. (3 balkc, 2 red, and 1 violet if I have the rigth schematic.) It could be disconnected there too.

BTW, the charging current to the battery does not go via the fuse block. So any issues with that would not be causing your main charging problem. The charging current goes from the alternator, through the bulkhead connector, to the welded splice, through the ammeter, back out the bulkhead connector, through the fusible link to the starter relay's big lug, and then to the battery. Since you have the car running and headlights, the connections from the battery all the way back through that chain of connections to the wleded splice are connected.
 
bigboijc13 had his car here for a few hours this morning. Like my car, the wiring was only good enough to sell the car. The wire from the alternator to the ammeter was cut Most of his wires are cracking from old age.
I think I got his stable. He can run the car and turn on the lights without the battery drawing down.

He needs the exact same thing my car did when I got it. He must track all wires and replace the cracking wires and verify every wire is where it belongs and is connected where it needs to be.
I am sure that most of us did just that.
 
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