Overcharging

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Christopher Lounsbery

Christopher Lounsbery

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I have a 1973 Swinger with a 318. About a week ago I had a crank no start issue, my ignition ballast took a dump. I replaced the ballast and cleaned the plugs , she started but now I am overcharging. I replaced the voltage regulator but no good. Everything was ok when I parked but after a week the gremlins came out ... any ideas?
 
Overcharging is VERY often caused by voltage drop in the ignition harness, if it's just a "bit over."

How bad is it? What voltage is the battery running, and is the ammeter pegged at higher RPM?

Generally, in no particular order:

1....Severe overcharge/ over voltage caused by field grounded on green wire (regulator) circuit, ether bad regulator, grounded green wire, or broken insulator in brush holder.

2...Bad voltage regulator

3...Bad battery or maybe it is just way down on charge. Charge it up (battery charger) and have it tested

4....Voltage drop problems. There is a LOT of this in these old cars. This is usually in the harness, but can also be because the VR is not grounded to battery potential

So.........if voltage only runs a little high, like 15--16V, and not severe, and if you think the battery is OK and charged, run these tests:

A....Turn key to run with engine off. leave all wiring connected. Connect voltmeter (back probe connector on field blue or at ballast---and stab other probe into the battery POS post. You are hoping for a very low reading, the lower the better. Much over .3V (3/10 of one volt) you need to investigate.

The functional path for power to the VR is .....battery---to starter relay "big stud" through fuse link.......through bulkhead connector (big red ammeter) to and through ammeter.....out on ammeter black........to welded splice (under dash) to ignition switch connector....through switch........back out connector on blue "ignition run" .....back through bulkhead connector...........and to underhood "run" loads, ignition, VR, alternator field, etc.

All of the points listed above can have a bad connection and cause volltage drop

B:..GROUND SIDE: Run these tests with engine warm, battery charged "normal" and at high idle to simulate med--low cruise speed RPM. Measure first with all accessories off, and again with headlights, heater, etc running.

So with engine running "fast idle" stab one probe into the mounting flange of the VR. Stab hard to get through paint, rust, etc. Stab other probe into top of battery NEG post. As in the first test, you are hoping for a very low reading, zero is perfect. If you get .2--.3V or worse, Clean VR mount and bolt holes, remount with star lock washers, and improve battery jumper to body
 
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67Dart273, I have a related question. On our old A-bodies, say everything is working properly, what level should the alternator be charging?

I've done the madd ammeter bypass, and I've added a relay to my ign, as you have suggested in many of these posts.
I'm now running a volt meter, and I'm reading 14.8 to 15.0 all the time.
Should I be worried?, or should I be running some of the tests you posted above?
 
I consider 15 to be "top of the limit" maybe push it to 15.5 sometimes. If you read the book, the electronic VR is temp compensated, and you must check it with engine warmed and battery "up" and normalized. The outline I posted above pretty much cover the possibilities. Sometimes a battery is a little "off" try swapping in a known good battery temporarily. The VR can be off but this is fairly rare. If you can't find anything else, replace that

But the key are the voltage drop checks...both ground and hot side

"How this works." The VR power (IGN) connection is also the "sensing," and this operates as a feedback loop, if the voltage the VR sees is low, it ramps it up until it's to the VR setpoint. Example. Let's say in the tests I outlined in the previous post, you have 2V drop measured. See below................

(By the way you can ALSO check the VR setpoint. With the car warm, running, and battery normalized, and if the voltage drop test gave up nothing, measure voltage from the blue "run" wire at thet ballast to the battery NEG post. If the VR is correct, it will read 13.8---14.4. And those figures are right out of the book, this chart out of the '72 Plymouth service manual)

Now, if you have 2V drop measured in the drop test, with the car running, you might well read 14.2 at the "ignition run" terminal with the engine running. So WHY does it produce 14.2+2 = 16.2 at the battery? SIMPLE. With the load on the alternator/ battery and the car running, the battery starts to sag, and there is 2V drop through the harness, so the VR ramps it up until the VR is seeing the 14.2 AT THE REGULATOR. But in order to do that, it must overcome the 2V harness drop (in this example) and so to get the VR IGN terminal up to the 14.2, it must ramp up voltage until that is so.........and the battery is boiling...............

regulator.jpg
 
I have the exact issue with my 75 Scamp. Started last fall. Came home one day and it wouldnt start. New battery then the overcharging started. I had the alternator checked. All good. Replaced, ballast, vr and module. Still overcharging. I think at the battery I was at 14. someting but, i cant remember. The gauge kept reading overcharge.
 
moparker said:
I think at the battery I was at 14. someting but, i cant remember. The gauge kept reading overcharge.
Click to expand...
If the battery is supplied power at 14 V, and the ammeter is showing heavy charge, then the battery is low.
The best thing to do is put it on a real charger. Especially if its a glass mat, give it a long slow charge.

Explanation, part 1.
When the engine is spinning the alternator fast enough, it produces power at the regulated voltage - that is 14.0 volts plus minus .8 V or so.
Everything connected to the alternator output should be at that voltage.
It's only at lower voltage in locations where current is flowing through resistance.

Explanation, part 2.
Most items, such as lamps, draw more current when power is supplied at higher voltage.
For example you may have noticed the headlights or dome light is brighter when the engine is running than when running on battery.
That's because the alternator supplies power around 14 V and the battery around 12.5 V.

A battery recharging does this too but draws less and less power as it gets close to full charge.
A dead battery connected to a charger or alternator at 14 Volts could draw 50 or 60 amps if the equipment could provide that much.
A fully charged battery connected to a charger or alternator at 14 Volts will draw close to 0 amps.
(The battery will develop a smalll surface charge over 13 Volts, but its real power will be at 12.8 Volts when the charger or alternator is disconnected and something is turned on.)
Photos in this post: Charging Battery with Alternator - Warning

Providing a battery with power over 15 Volts will cook it (boil off the acid) - that's over charging.
Providing a battery with power under 14 Volts can also cause it to overheat if its drawing a lot of current.
So if you see the ammeter indicating high current (20+ amps) to the battery for more than a few minutes, that's an indication of a problem.
See photos linked above.
A glass mat (optima) battery does not disapate heat well. They need to be charged at a slow rate or they will be damaged.
 
Either the battery was low or bad battery, like sulfated
 
Ok. Thanks for all your help. I feel a little silly. I had the battery tested and charged at a chain location and it tested fully charged and good. I brought my carbon pile tester home and it shows good but still low. I put the battery on a high amp charger and the battery came fully back. Now everything is operating correctly. The trickle chargers these supply houses use do not properly charge the battery. Live and learn my friends
 
All good intel.
Most of us know, but worth putting it out there, trickle chargers don't maintain absorbed glass mat (AGM) batteries.
Gotta follow their procedures.
 
Christopher Lounsbery said:
Trickle chargers are not recommended for most batteries nowadays.
Click to expand...
why does everyone replace the ballast for EVERY electrical malady? The ballast has NOTHING to do with charging, it is only there tor educe primary voltage to the coil so it doesn't burn itself up. Nothing else. If it doesn't start and die when you release the key, the ballast IS NOT the problem!
 
volaredon said:
why does everyone replace the ballast for EVERY electrical malady? The ballast has NOTHING to do with charging, it is only there tor educe primary voltage to the coil so it doesn't burn itself up. Nothing else. If it doesn't start and die when you release the key, the ballast IS NOT the problem!
Click to expand...
 
Volaredon,
Back as a young mechanic, the boss used to have us replace the Ballast Resistors on most any Chrysler product that was a "no start".
The thought was that if it wasnt bad then, it will bad be later.
A sort of cheap preventive maintenance.
They seemed to go bad quite often back then.
Joe
 
Joey4speed said:
Volaredon,
Back as a young mechanic, the boss used to have us replace the Ballast Resistors on most any Chrysler product that was a "no start".
The thought was that if it wasnt bad then, it will bad be later.
A sort of cheap preventive maintenance.
They seemed to go bad quite often back then.
Joe
Click to expand...
That is why I have carried a spare ballast in my car since 1970 they die at the worst times , but are an easy fix
 
Nat said:
That is why I have carried a spare ballast in my car since 1970 they die at the worst times , but are an easy fix
Click to expand...
I've owned nothing but Mopar since 1983, and always had a spare with me but only ever had a couple of them die on me
 
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