Charging system voltage high

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mod38-1

mod38-1

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I just replaced my alternator because of a bad bearing in old one. I thought I would check voltage with new alternator and it is showing 15.4 volts at the battery. I tried my spare voltage regulator I have and it is the same. Voltage regulator is grounded good. Wires between alternator and voltage regulator test good. I found if voltage regulator is taken out of system alternator does not charge at all so I do not think it has anything to do with voltage regulator. I have also tried a known good battery also with no change. I searched and found several other threads with the same issue just no one ever posted if they found problem or not. Thanks
 
Make the following checks, and if they show nothing, it's either the regulator or the battery. What you will be checking for is "voltage drop" both across the ground and "hot" side of things.

Get the car running, and jack up the idle to simulate "low to medium cruise." Turn off all accessories.

Take your meter on LOW volts, and stab one probe directly onto the battery neg. post. Stab the other probe directly onto the regulator case, and make sure you penetrate the paint/ chrome.

What you are looking for is a VERY low reading, the lower the better, zero would be perfect. Anything over .2V (two tenths of a volt) shows you have a grounding problem

Now check the "hot" side. What you may have here is a bad connection in the path from the battery -- fuse link-- bulkhead connetor, --through the ammeter circuit -- through the ignition switch connector, the switch contacts, and back out the switch connector -- back out the bulkhead connector.

So stab one probe directly onto the battery positive post. The other probe goes to "ignition run" IE the traditional dark blue which feeds ignition voltage to the ignition system and regulator. It might be that the ballast resistor is the closest you can come.

Once again, you are looking for a low reading, and a difference of more than .2 shows a drop problem in this circuit.

Regulators --that is, electronic ones -- seldom act in this manner. I'm betting it's either the ground or ign circuit that's causing you grief

On my 67, there was a ONE VOLT drop through the bulkhead on "ignition run." This was causing considerable overcharging.

Another way to check the "hot" circuit is to turn the key to "run," engine off. Put your probes on battery positive, and the "ignition run" supply. You are now measuring the voltage drop directly in that circuit.

Also, more and more, we hear of owners with "bulkhead connector" troubles. It might just pay to pull it apart, inspect and clean it, replace any bad terminals, consider feeding the big alternator/ battery feed wires "straight through" and read the "Mad Electrical" article on the subject:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

which came from here:

http://www.madelectrical.com/electrical-tech.shtml
 
Just for the sake of saying you tried it. Switch the locations of the 2 wires on the alternator. I remeber seeing something about how the aftermarket was rewiring the brush trminals or inside the units.
 
RedFish said:
Just for the sake of saying you tried it. Switch the locations of the 2 wires on the alternator. I remeber seeing something about how the aftermarket was rewiring the brush trminals or inside the units.
Click to expand...

Red, PLEASE DON'T. What happens here, is that sometimes, due to using old alternator frames, or just plain defective brush holders, one brush is grounded.

So......

IF YOU WERE lucky enough to get the blue "ignition" wire hooked to the ungrounded brush, and if this is the trouble, you will now......

be hooking.....

the blue field wire directly to GROUND through the grounded brush.

Since the ignition circuit is not fused..........

this will result in the illegal release of SMOKE, and the EPA will declare your neighborhood a toxic cleanup area.
 
mod38-1 said:
I just replaced my alternator because of a bad bearing in old one. I thought I would check voltage with new alternator and it is showing 15.4 volts at the battery. I tried my spare voltage regulator I have and it is the same. Voltage regulator is grounded good. Wires between alternator and voltage regulator test good. I found if voltage regulator is taken out of system alternator does not charge at all so I do not think it has anything to do with voltage regulator. I have also tried a known good battery also with no change. I searched and found several other threads with the same issue just no one ever posted if they found problem or not. Thanks
Click to expand...



Maybe I am missing something here but if 15 to 16 volts is normal and you have 15.4 then what are you looking for?
 
67Dart273 said:
Make the following checks, and if they show nothing, it's either the regulator or the battery. What you will be checking for is "voltage drop" both across the ground and "hot" side of things.

Get the car running, and jack up the idle to simulate "low to medium cruise." Turn off all accessories.

Take your meter on LOW volts, and stab one probe directly onto the battery neg. post. Stab the other probe directly onto the regulator case, and make sure you penetrate the paint/ chrome.

What you are looking for is a VERY low reading, the lower the better, zero would be perfect. Anything over .2V (two tenths of a volt) shows you have a grounding problem

Now check the "hot" side. What you may have here is a bad connection in the path from the battery -- fuse link-- bulkhead connetor, --through the ammeter circuit -- through the ignition switch connector, the switch contacts, and back out the switch connector -- back out the bulkhead connector.

So stab one probe directly onto the battery positive post. The other probe goes to "ignition run" IE the traditional dark blue which feeds ignition voltage to the ignition system and regulator. It might be that the ballast resistor is the closest you can come.

Once again, you are looking for a low reading, and a difference of more than .2 shows a drop problem in this circuit.

Regulators --that is, electronic ones -- seldom act in this manner. I'm betting it's either the ground or ign circuit that's causing you grief

On my 67, there was a ONE VOLT drop through the bulkhead on "ignition run." This was causing considerable overcharging.

Another way to check the "hot" circuit is to turn the key to "run," engine off. Put your probes on battery positive, and the "ignition run" supply. You are now measuring the voltage drop directly in that circuit.

Also, more and more, we hear of owners with "bulkhead connector" troubles. It might just pay to pull it apart, inspect and clean it, replace any bad terminals, consider feeding the big alternator/ battery feed wires "straight through" and read the "Mad Electrical" article on the subject:

http://www.madelectrical.com/electricaltech/amp-gauges.shtml

which came from here:

http://www.madelectrical.com/electrical-tech.shtml
Click to expand...

Thanks for the fast and accurate reply. What I found was 1.6v between positive post of battery and ignition side of ballast resistor. If I run a jumper wire between positive post of battery and ignition side of ballast the charging system voltage with it running is 14.2v. So it looks like now I need to chase a wiring problem in the ignition circuit. My car already has the added wire from alternator to starter relay to bypass most of bulkhead connector issues per the write up on allpar.
 
Yup, the right track. My first suspect would be the bulkhead connector, next on the list would be the connector on the ign switch, and last the switch itself.

To see where you "are" after you think you've fixed it, check it first before, then after, with the engine off as I outlined.
 
KP said:
Maybe I am missing something here but if 15 to 16 volts is normal and you have 15.4 then what are you looking for?
Click to expand...

15-16 volts is NOT normal. "Normal" is 13.8-14.2, (depending on whose book you read) plus or minus allowance for temperature of the regulator, battery condition, etc.
 
Well after checking stuff for most of day today I am still no closer to problem. I checked all bulkhead connectors and the are good. While bulkhead connectors were apart I unhooked everything that the blue wire that goes from alt to voltage regulator goes to and performed a voltage drop test on that circuit and it had no voltage loss and it lit a halogen light good at all ends,so I think that wiring is good. I checked voltage loss across ignition swicth with car running and it has battery voltage going in on pink wire and only loses about .2v coming out on blue wire. Voltages with car running are 15.2-15.4 at battery and battery end on back of alternator,14.2 at blue wire at ballast resistor,voltage regulator,and alternator field. Blue wire that goes from ignition switch to underhood loses about 1v between ignition switch and components but that wire feeds ballast resistor,control module,goes to voltage regulator and alternator. I also charged battery for a hour to see if that would change anything and it did not. Last thing I did was put a jumper wire between battery in and battery out of ignition switch and that also did not change anything.
 
It cant over charge if the wiring and the voltage regulator are good unless the voltage regulator is not working properly.
 
Forgot to add that I went and bought a new voltage regulator today and it actually charges more (15.8v) with new regulator
 
mod38-1 said:
Blue wire that goes from ignition switch to underhood loses about 1v between ignition switch and components but that wire feeds ballast resistor,control module,goes to voltage regulator and alternator..
Click to expand...

THAT IS your big clue and THAT IS the area of the problem.

The path for that wire is from the battery, fuse link, BULKHEAD CONNECTOR (hint hint) to the ammeter circuit, the ignition switch connector, ignition switch, back OUT the ignition switch connector, BACK through the BULKHEAD CONNECTOR, and to the points that it fees, IE ignition, regulator, alternator field, electric choke if used.

One volt is a LOT. Go down the path you started, ---disconnect the ignition from the dark blue and apply a big load, about 5 amps or so.

Then go backwards from the engine bay, check the INSIDE of the bulkhead connector, both the battery feed and the dark blue ignition wire.

Take the bulkhead apart and inspect and clean it.

IF YOU CAN NOT or "will not" fix the problem, one way out is to install a good quality relay, fuse the supply to it, and use the dark blue to do NOTHING but to "key" the relay. Then feed all the loads in the engine bay off the relay contacts

So feed the relay with a good fuse, located away from engine heat, supplied from the starter relay stud. Feed the output from the contacts to your old "dark blue." You'll have to break the dark blue after it comes out of the bulkhead and BEFORE it splits off to alternator, ignition, and regulator.

Wire one coil connection to ground. Wire the other coil connection to your old dark blue coming out of the bulkhead.
 
67Dart273 said:
THAT IS your big clue and THAT IS the area of the problem.

The path for that wire is from the battery, fuse link, BULKHEAD CONNECTOR (hint hint) to the ammeter circuit, the ignition switch connector, ignition switch, back OUT the ignition switch connector, BACK through the BULKHEAD CONNECTOR, and to the points that it fees, IE ignition, regulator, alternator field, electric choke if used.

One volt is a LOT. Go down the path you started, ---disconnect the ignition from the dark blue and apply a big load, about 5 amps or so.

Then go backwards from the engine bay, check the INSIDE of the bulkhead connector, both the battery feed and the dark blue ignition wire.

Take the bulkhead apart and inspect and clean it.

IF YOU CAN NOT or "will not" fix the problem, one way out is to install a good quality relay, fuse the supply to it, and use the dark blue to do NOTHING but to "key" the relay. Then feed all the loads in the engine bay off the relay contacts

So feed the relay with a good fuse, located away from engine heat, supplied from the starter relay stud. Feed the output from the contacts to your old "dark blue." You'll have to break the dark blue after it comes out of the bulkhead and BEFORE it splits off to alternator, ignition, and regulator.

Wire one coil connection to ground. Wire the other coil connection to your old dark blue coming out of the bulkhead.
Click to expand...

Thanks again for everyones replies. I need to add that it only loses that 1v with the engine running. With the engine off and key on the blue wire at voltage regulator,ballast resistor is the same as battery voltage.
 
mod38-1 said:
I need to add that it only loses that 1v with the engine running. With the engine off and key on the blue wire at voltage regulator,ballast resistor is the same as battery voltage.
Click to expand...


You may not have enough (or any) load on the circuit with the engine off. THIS IS your problem if you have measured that drop at those two points. You just need to figure out where it is materializing.

You already jumpered across it and proved the voltage went back down, so you are in the right area.
 
That alternator puts out 13.8 - 15.4 volts. That is what it does. If it had twelve volts at the battery, how would it ever charge? There is nothing wrong with your charging system that I see.
 
Mopar to ya said:
That alternator puts out 13.8 - 15.4 volts. That is what it does. If it had twelve volts at the battery, how would it ever charge? There is nothing wrong with your charging system that I see.
Click to expand...

Screw it
 
I had the same problem and it turned out to be the ign. switch. voltage drop between battery feed and ign. on circuit. 15.7 volts will eventually boil the battery dry!
 
I had the same problem and it was a bad battery that wouldent take a full charge and the alternator kept trying to charge it
 
Listen to 273. wiring, bad battery, or one field grounded. I have had them put out 18+ in that situation.
 
1wild&crazyguy said:
and by the time it put out 18volts, the alternator was junk..
Click to expand...

Actually.......

In the early '70's you could buy a little box, had a switch and electrical outlet on the box

You would throw the switch and here's what it did.....

The switch "full fielded" the alternator, as well as disconnecting the output from the battery, and switching the output to the electrical outlet.

Then you plugged in your 120V trouble light, etc, and revved the engine until the lamp was "bright enough."

I'd love to see specs on how many people....

blew up their alternator

Cooked that stupid switch trying to handle 50-60 amps

tried to run AC motors or transformer powered devices

or just "in general" became stranded......
 
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