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Too Much Voltage #2714326
11/09/19 07:18 PM
11/09/19 07:18 PM
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Mesa, Arizona
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dart4forte Offline OP
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First, I hate wiring and electrical. 1974 Dodge D100. So, installed a new Autometer voltmeter. Wired into the ignition feed and wired to a good ground. Fired it up and it was reading 12-14 volts at idle and 14.5 at cruise. Anyway yesterday afternoon I was cruising down the freeway and noticed the VM reading 16.5, took the offramp and came to a stop. It read 16 at idle. Turned on the lights and it made no differance.

Today I replaced the voltage regulator with a spare I had. Still reads high. Switched alternators and I get the same. Went through and made sure all my grounds are tight. I even added a frond wire to one of the mounting bolt for the regulator. Cleaned up the ground foe the batter6 cable. Had the battery checked, it showed it had a bad cell. So, new battery. Came home and put it all together. Now, it idles at 14-14 volts and when driving it’s back to 16-17 volts.

Any suggestions?


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Abe Lincoln
Re: Too Much Voltage [Re: dart4forte] #2714352
11/09/19 09:04 PM
11/09/19 09:04 PM
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Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition.
Next I would check the reading across the battery. it "should " be very close to the ign terminal reading.
if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests
Report back and we'll got from there beer

Re: Too Much Voltage [Re: TJP] #2714361
11/09/19 09:39 PM
11/09/19 09:39 PM
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dart4forte Offline OP
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Originally Posted by TJP
Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition.
Next I would check the reading across the battery. it "should " be very close to the ign terminal reading.
if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests
Report back and we'll got from there beer


Thanks


“So if it’s on the internet it must be true”

Abe Lincoln
Re: Too Much Voltage [Re: TJP] #2714362
11/09/19 09:40 PM
11/09/19 09:40 PM
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dart4forte Offline OP
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Originally Posted by TJP
Check the Ign. terminal on the regulator. It "senses" the available voltage and energizes the field windings in the alternator to bring the voltage up. A low reading at the terminal will cause an overcharge condition.
Next I would check the reading across the battery. it "should " be very close to the ign terminal reading.
if not try removing and reinstalling the bulkehead connector at the firewall and repeat the above tests
Report back and we'll got from there beer


Am I checking with a volt meter?


“So if it’s on the internet it must be true”

Abe Lincoln
Re: Too Much Voltage [Re: dart4forte] #2714381
11/09/19 10:55 PM
11/09/19 10:55 PM
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Andrewh Offline
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yes use a volt meter.
basically you are checking for a voltage difference in the sensing line or the field line.

1 field line goes to the vr the other ties back into the key on power from the ign 1 on the key.

here is how I look for voltage drops.

with the car on run, but not running.
you check with the voltmeter using the battery ground.
check against the pos of the battery, see what the voltage reads.
then check voltage at the sensing line of the VR.
Then check voltage at the field of the alt. with the vr plug pulled, (assuming this is a dual field alt using the later triangle plug vr), one of the fields will be 0, the other should be battery voltage.
you can then trace back to the bulkhead to see if that is causing the issue or a bad connection somewhere else.

you can also transfer the ground to the body of the vr as well when checking the sensing line voltage and to the body of the alt for the field to see if there is a ground issue.

generally speaking I would bet you will see almost 1 volt drop meaning you need to clean up the bulkhead connector or find the bad connection.
if swaping the ground gives you a bigger volt diff, then you have a bad ground somewhere.

Re: Too Much Voltage [Re: dart4forte] #2714397
11/09/19 11:54 PM
11/09/19 11:54 PM
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Do you trust that Autometer gauge to be accurate now?
Check it out first against a real good V.O.M. scope twocents
I've had to many expensive Autometer mechanical race gauge that where NOT accuarte down


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Too Much Voltage [Re: Andrewh] #2714428
11/10/19 03:29 AM
11/10/19 03:29 AM
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dart4forte Offline OP
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Originally Posted by Andrewh
yes use a volt meter.
basically you are checking for a voltage difference in the sensing line or the field line.

1 field line goes to the vr the other ties back into the key on power from the ign 1 on the key.

here is how I look for voltage drops.

with the car on run, but not running.
you check with the voltmeter using the battery ground.
check against the pos of the battery, see what the voltage reads.
then check voltage at the sensing line of the VR.
Then check voltage at the field of the alt. with the vr plug pulled, (assuming this is a dual field alt using the later triangle plug vr), one of the fields will be 0, the other should be battery voltage.
you can then trace back to the bulkhead to see if that is causing the issue or a bad connection somewhere else.

you can also transfer the ground to the body of the vr as well when checking the sensing line voltage and to the body of the alt for the field to see if there is a ground issue.

generally speaking I would bet you will see almost 1 volt drop meaning you need to clean up the bulkhead connector or find the bad connection.
if swaping the ground gives you a bigger volt diff, then you have a bad ground somewhere.



I should also add the truck idles ok but when put in either reverse or drive the engine dies.


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Abe Lincoln
Re: Too Much Voltage [Re: Andrewh] #2714457
11/10/19 09:55 AM
11/10/19 09:55 AM
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Mattax Offline
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Removing the connector from the regulator creates an open circuit.
No current flows.
The voltage at both connector terminals should be within tenths of the battery.
The only drop would be from the current flowing to the ignition, which is only a couple amps.

In this situation, it probably makes more sense to measuring voltage at the alternator output stud to the regulator input with the engine running.
The closest locations to measure the votlage being sensed by the regulator while running are the alternator brush with the 'ignition' wire, and the ballast resistor connection with the same.
The 'ignition' or 'run' wires are usually dark blue or dark blue with a white tracer. But being a truck, it might be different. Later trucks used a different color, but my guess is '74 is the same as cars of those years.

If the voltage developed by the alternator increases with increasing rpm and vica versa, then it is almost certainly a regulation issue. A small variance at low rpm is normal. But going above 15 Volts is not.
If the second brush (usually connected to the green wire) gets grounded, then there is no voltage regulation. So check the brush terminal's insulator and also the insulation on the green wire to the regulator. If that's not it, then suspect the regulator.

Re: Too Much Voltage [Re: Mattax] #2714459
11/10/19 10:05 AM
11/10/19 10:05 AM
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Mattax Offline
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The regulator works like this.

Voltage of the Ignition Wire (J) is internally measured by the transistors.
If it the voltage is low, the connection to ground for the rotor is completed.
Current then flows through the rotor windings creating a spinning electromagnetic field.

If the voltage in the Ignition Wire (J) is high enough, a tiny current is used to break the rotor's connection to ground.

1970-VR-corrected-MT-flow.png
Re: Too Much Voltage [Re: Mattax] #2714530
11/10/19 01:32 PM
11/10/19 01:32 PM
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TJP Offline
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Originally Posted by Mattax
The regulator works like this.

Voltage of the Ignition Wire (J) is internally measured by the transistors.
If it the voltage is low, the connection to ground for the rotor is completed.
Current then flows through the rotor windings creating a spining electromagnetic field.

If the voltage in the Ignition Wire (J) is high enough, a tiny current is used to break the rotor's connection to ground.


Nice diagram beer

Re: Too Much Voltage [Re: TJP] #2714574
11/10/19 04:54 PM
11/10/19 04:54 PM
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dart4forte Offline OP
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Ok, dug out my voltmeter. Static voltage on the battery is 12.7 volts. Fired the motor and I get 18.5 at idle. Checked the alternator and at idle I’m getting 18.5, run the motor up at around 1500 rpm and the reading was 22 volts. Took the alternator off and ran down to Orielys. On a short test the machine showed 16.5 volts. Overall the alternator tested bad.

Last edited by dart4forte; 11/10/19 04:56 PM.

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Abe Lincoln
Re: Too Much Voltage [Re: dart4forte] #2714602
11/10/19 07:01 PM
11/10/19 07:01 PM
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You did good, test, test and test some more until you whup Murphys butt upl


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Re: Too Much Voltage [Re: Cab_Burge] #2714902
11/11/19 06:46 PM
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Ok, changed out the alternator. Fired it up and it now runs ar idle 13.5 to 14.5 however when the rpms go up it goes to 16 volts. I went ahead a pulled the bulkhead plugs. As suspected both the red white going in was burn’t at the spade and the same for the black wire that goes to the alternator. I have the bulkhead soaking in Evaporust. I did this on a 65 Chrysler I had and the contacts came out squeaky clean. I may just go ahead and replace both the red and black wires, drill out the bulkhead fitting and run the wires through the bulkhead.


Last edited by dart4forte; 11/11/19 06:48 PM.

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Abe Lincoln
Re: Too Much Voltage [Re: dart4forte] #2715159
11/12/19 03:22 PM
11/12/19 03:22 PM
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I had a similar problem after I painted my Charger. I cleaned up the grounds and added a ground wire to the voltage regulator and all is well now.

Re: Too Much Voltage [Re: 74RALLYE] #2715188
11/12/19 05:33 PM
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Check the plug on the ignition switch. I have seen quite a few melted causing issues. My 77 plymouth had a problem with overcharging and it was a melted blue wire at the bottom of the column grounding out.

Re: Too Much Voltage [Re: mopars4ever] #2715318
11/13/19 12:45 AM
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dart4forte Offline OP
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Originally Posted by mopars4ever
Check the plug on the ignition switch. I have seen quite a few melted causing issues. My 77 plymouth had a problem with overcharging and it was a melted blue wire at the bottom of the column grounding out.


Plug on the ignition switch?


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Re: Too Much Voltage [Re: dart4forte] #2715319
11/13/19 01:00 AM
11/13/19 01:00 AM
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Originally Posted by dart4forte
Originally Posted by mopars4ever
Check the plug on the ignition switch. I have seen quite a few melted causing issues. My 77 plymouth had a problem with overcharging and it was a melted blue wire at the bottom of the column grounding out.


Plug on the ignition switch?

On the steering column is a flat plug. The Blue wire on my sons 1974 D200 was burnt. I cut them out and put a bullet connector inline.


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Re: Too Much Voltage [Re: Dave_J] #2715349
11/13/19 09:15 AM
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As said the plug is near the base of the column. A common fail point on ignition switches.

Re: Too Much Voltage [Re: mopars4ever] #2715381
11/13/19 11:43 AM
11/13/19 11:43 AM
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i have repaired many of those connectors because of a "melty" condition over the years.
beer

Re: Too Much Voltage [Re: moparx] #2715486
11/13/19 06:55 PM
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Ok, all up and running. I get 14 volts ar idle and 14.5 at cruse. Meter bounces a bit which give me reason to think there’s a hiccup in there. Got home ant had a crappy idle, finally died. Restarted now it dies when I put it in gear. Given I drove the truck hitting bumps leads me toward the bulkhead connector. At idle the battery is getting a charge around 14 voltsI’ll go out and check tomorrow. Also, since we changed out the steering column I’ll be checking that wiring as well.


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