Barracuda Challenger Forum

Author Topic: 16.4 volts at the battery  (Read 4609 times)

Offline Bullitt-

  • Permanent Resident
  • *******
  • Posts: 12082
  • Better Things To Come Member Since 2/16/06
Re: 16.4 volts at the battery
« Reply #30 on: May 09, 2017 - 12:02:25 AM »
I'd be looking at the Blue wire to the voltage regulator that I think is the same power that is supplied for the ignition.
As I understand it that is what the VR monitors to see if the battery needs more or less charging (should be same as battery voltage) so if it's not connected well the VR is fooled into thinking it should make the alternator send more juice.
RE: the ground cable, I'd think if it were a problem cranking the car would be an issue. 
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
Having Trouble Uploading Pics?




Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #31 on: May 09, 2017 - 05:11:07 AM »
Yeah that blue wire is the one that also feeds the choke and a couple other things.....and connects to the one field connector on the alternator.....thats the one reading 14.8 volts and I cant see any issues with it....

Offline Bullitt-

  • Permanent Resident
  • *******
  • Posts: 12082
  • Better Things To Come Member Since 2/16/06
Re: 16.4 volts at the battery
« Reply #32 on: May 09, 2017 - 08:37:57 AM »
It's loosing a volt somewhere ... recently saw a post that someone had a Ammeter that had high resistance, also this power runs trough the steering column harness & plug which is a week link.

Do you have a ground strap from the motor to the firewall?... don't know if not having one would cause this but the factory put one there for a reason..
Wade  73 Rallye 340..'77 Millennium Falcon...13 R/T Classic   Huntsville, AL
Having Trouble Uploading Pics?


Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #33 on: May 09, 2017 - 10:14:29 AM »
It's loosing a volt somewhere ... recently saw a post that someone had a Ammeter that had high resistance, also this power runs trough the steering column harness & plug which is a week link.

Do you have a ground strap from the motor to the firewall?... don't know if not having one would cause this but the factory put one there for a reason..

I have a ground strap from the fireall/ecu to the motor (valve cover bolt) and one from the firewall/VR to the same bolt.  I ran a separate temporary jumper wire from the VR/firewall to the battery negative and no change.

My ammeter has been bypassed (one of the first things I did years ago).


Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #34 on: May 14, 2017 - 01:53:09 PM »
So looking at my fusible link connector I saw that it looked like it had melted a little



I pulled it apart and found this:



I was thinking maybe THAT was contributing to the high voltage reading......
I replaced the spade with a new one...crimped and a little solder....reassembled.

No luck.  Same high readings.

Even disconnected the choke, no change.

Back to the drawing board.

At this point all I can figure is that the problem must be on the bulkhead or dash side of the car.
« Last Edit: May 14, 2017 - 02:06:28 PM by shadango »

Offline 73plymouth440

  • Jr. Member
  • **
  • Posts: 13
Re: 16.4 volts at the battery
« Reply #35 on: May 14, 2017 - 09:41:05 PM »
Was having the same problem with my 73 barracuda although my stock gage was showing an over charge. For me not was  from ncorrectly connecting the wire to my alternatorafter thathad been replaced.
73 barracuda 440 (in progress)
66 barracuda 273 commando  (for sale to a loving home, needs lots of work)

Offline 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1635
Re: 16.4 volts at the battery
« Reply #36 on: May 15, 2017 - 10:38:12 AM »
I'd be looking at the Blue wire to the voltage regulator that I think is the same power that is supplied for the ignition.
As I understand it that is what the VR monitors to see if the battery needs more or less charging (should be same as battery voltage) so if it's not connected well the VR is fooled into thinking it should make the alternator send more juice.
RE: the ground cable, I'd think if it were a problem cranking the car would be an issue.

 :iagree: The blue wire is where the regulator senses system voltage and when functioning properly, will try to field the alternator to maintain (regulate) 14 volts +- .2 volts. Raise the idle when testing the alternator to 1200-1500 rpm. The amperage output at idle too low to test properly, especially a roudback alternator. Based on the testing that you have done already, it appears that your voltage regulator and alternator are working, but there is a voltage drop on the blue wire feeding power to the regulator, throwing the alternator output voltage out of range. Do you have a hand held digital voltmeter for testing?
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #37 on: May 15, 2017 - 12:15:07 PM »
:iagree: The blue wire is where the regulator senses system voltage and when functioning properly, will try to field the alternator to maintain (regulate) 14 volts +- .2 volts. ......<snip>......but there is a voltage drop on the blue wire feeding power to the regulator, throwing the alternator output voltage out of range. Do you have a hand held digital voltmeter for testing?

Yes I have a meter...

But  HOW do I test it?   What am I looking for? 

I had previously tested the blue/purple wire at the VR and it was lower in voltage....but should I be testing that when connected to the VR or disconnected?  With engine running or not?

All the connectors seem ok...choke connector, ballast connector, etc
« Last Edit: May 15, 2017 - 12:21:47 PM by shadango »

Offline 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1635
Re: 16.4 volts at the battery
« Reply #38 on: May 15, 2017 - 08:38:37 PM »
Yes I have a meter...

But  HOW do I test it?   What am I looking for? 

I had previously tested the blue/purple wire at the VR and it was lower in voltage....but should I be testing that when connected to the VR or disconnected?  With engine running or not?

All the connectors seem ok...choke connector, ballast connector, etc

First thing is I'm sorry you have been dealing with this overcharging issue for so long! :-\
I'll explain how to test your charging system for you. 40+ years as a service professional, I do this on a daily basis. You are looking to locate the source of the voltage drop (resistance) in the charging system. We will test the charging system running and loaded, VR connected with the engine rpm set at 1200-1500 rpm for accuracy.
 To start off; In a perfect world there will be no difference between the battery positive terminal voltage and the voltage reading at the blue wire (at the VR).On the ground side, the VR attaching ground screw, and battery negative terminal. The alternator positive output terminal and the battery + terminal and last the alternator case ground and the battery negative terminal. Does this make sense?
« Last Edit: May 15, 2017 - 10:31:25 PM by 734406pk »
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #39 on: May 18, 2017 - 10:50:39 AM »
 So I should use the pin method and see what the vr is seeing when plugged in? Or disconnect and check?

Offline 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1635
Re: 16.4 volts at the battery
« Reply #40 on: May 18, 2017 - 08:04:20 PM »
So I should use the pin method and see what the vr is seeing when plugged in? Or disconnect and check?

Ok when your ready we can start at the beginning. Completely reconnect the charging system so it's ready to go, then start the engine and set the idle to 1200-1500 rpm. Turn on all the accessories in the car, headlights on high beam, interior light etc. Leave the flashers/blinker off. We want a constant load. Now take these readings:

A- Battery voltage. Positive test lead on the positive battery POST (not the battery wire terminal). Negative test lead to the negative battery POST (not the wire terminal. Write down the voltage reading as A.

If your digital volt meter doesn't auto-range, select 4 Volt DC scale for better accuracy. Then-

B- Alternator output ground side voltage drop: Connect the negative test lead to a clean bare metal spot on the alternator housing. Connect the positive test lead to the Negative battery post, (not the battery wire terminal). Write down the reading as B.

C- Alternator output positive side voltage drop: Connect the positive test lead to the output (+) terminal on the alternator, attach the negative test lead to the battery Positive Post. Write down this reading as C.

Here's a how to video: https://www.youtube.com/watch?v=_B0LjwQbUbg

Turn the idle speed back down and shut off all the accessories. Turn off the engine. Post your readings when you have a chance.  :thumbsup:
« Last Edit: May 19, 2017 - 12:40:12 AM by 734406pk »
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline shadango

  • Resident
  • *****
  • Posts: 3843
Re: 16.4 volts at the battery
« Reply #41 on: May 19, 2017 - 09:10:54 AM »
Ok when your ready we can start at the beginning. Completely reconnect the charging system so it's ready to go, then start the engine and set the idle to 1200-1500 rpm. Turn on all the accessories in the car, headlights on high beam, interior light etc. Leave the flashers/blinker off. We want a constant load. Now take these readings:

A- Battery voltage. Positive test lead on the positive battery POST (not the battery wire terminal). Negative test lead to the negative battery POST (not the wire terminal. Write down the voltage reading as A.

If your digital volt meter doesn't auto-range, select 4 Volt DC scale for better accuracy. Then-

B- Alternator output ground side voltage drop: Connect the negative test lead to a clean bare metal spot on the alternator housing. Connect the positive test lead to the Negative battery post, (not the battery wire terminal). Write down the reading as B.

C- Alternator output positive side voltage drop: Connect the positive test lead to the output (+) terminal on the alternator, attach the negative test lead to the battery Positive Post. Write down this reading as C.

Here's a how to video: https://www.youtube.com/watch?v=_B0LjwQbUbg

Turn the idle speed back down and shut off all the accessories. Turn off the engine. Post your readings when you have a chance.  :thumbsup:

Thanks for this!  Will test as soon as I can.

Offline 73_Cuda_4_Me

  • Jr. Member
  • **
  • Posts: 358
Re: 16.4 volts at the battery
« Reply #42 on: May 19, 2017 - 09:15:31 AM »
 :iagree:   :worshippy

Others may wonder about the procedure listed by 734406pk, but they are right on.. it's measuring the voltage 'drop' from end to end of each circuit... all wiring and connections provide a resistance to current flow.. the more resistance in the circuit, the more drop there will be from one end to the other... by using low voltage scale on meter, you can read what the difference in voltage is from one end of the circuit to the other... the higher the voltage reading end-to-end, the more resistance there is in that circuit... the worse the voltage drop is... BAD

Ideally, you want ZERO volt readings (no resistance end to end) on the circuits described, but there will always be some resistance in the wires/connections.

 :thumbsup:
1973 Plymouth Cuda BS23H3B567783

R11 V6X EN2
M21 M25 M31 M88 N41 N42
V1X U B41 C56 G37 J54
JY9 A6X9 0 703 501616
E55 D34 BS23 H3B 567783

Offline 734406pk

  • Andy
  • Sr. Member
  • ****
  • Posts: 1635
Re: 16.4 volts at the battery
« Reply #43 on: May 19, 2017 - 09:53:11 AM »
:iagree:   :worshippy

Others may wonder about the procedure listed by 734406pk, but they are right on.. it's measuring the voltage 'drop' from end to end of each circuit... all wiring and connections provide a resistance to current flow.. the more resistance in the circuit, the more drop there will be from one end to the other... by using low voltage scale on meter, you can read what the difference in voltage is from one end of the circuit to the other... the higher the voltage reading end-to-end, the more resistance there is in that circuit... the worse the voltage drop is... BAD

Ideally, you want ZERO volt readings (no resistance end to end) on the circuits described, but there will always be some resistance in the wires/connections.

 :thumbsup:

Thank You!  :2thumbs: This method for testing voltage drop may be a little tough to understand at first (it was for me!) but its incredibly accurate. The plan is to test the entire charging system this way.
1973 Challenger 440 6 pack auto 3.91 rear
2012 Dodge Ram 3500 dually 6.7 Cummins Fleece EFI Live
1973 Challenger 318 2bbl auto 2.73 rear 22.5 mpg RIP
1970 Challenger TA 340 4bbl auto-Sold and sad
1999 Dodge Ram 3500 dually 5.9 Cummins Fleece tuned VGT-sold
1995 Kawasaki ZX1100E & still alive

Offline 73_Cuda_4_Me

  • Jr. Member
  • **
  • Posts: 358
Re: 16.4 volts at the battery
« Reply #44 on: May 19, 2017 - 11:31:21 AM »
The only thing I would add to this is that IF you get a large voltage drop when reading to either of the battery posts, the first thing to check is the battery cable to battery post connections...

they always seem to 'corrode' first, and ground post faster than positive post... (it will build up an oxidized layer between the inside connector surfaces and post surfaces). Use a battery terminal cleaner/wire brush to remove the corrosion, and apply some dielectric grease to the connectors when re-attaching them, to help prevent buildup in the future.
1973 Plymouth Cuda BS23H3B567783

R11 V6X EN2
M21 M25 M31 M88 N41 N42
V1X U B41 C56 G37 J54
JY9 A6X9 0 703 501616
E55 D34 BS23 H3B 567783