Possible voltage issue

[slapstickjim]

I bought this 76 dart this winter. I been going overr it now that's it's nice been driving it. Looking it over( wiring) I saw nothing crazy. Like cut ,spliced wires etc. I installed a volt gauge and noticed it was a tad over 14,. As my old eyes from 3 ft saw without readers lol. I drove it the other night and headlights were going dim bright dim bright. So I check at battery and I am getting 15.6 volts.

Should I be concerned???

I looked over things a few hours and tried stuff after each trial I would start car and still 15.7. What I did. Used regulator, new regulator, ground wire from regulator mounting to batery, ground wire engine to body installed, new starter relay, unhooked rehooked alt wires, jumper cable battery to body, bulk head connectors from engine side unhooked no corrosion and cleaned with brush and hooked back up. No wires seem cut frayed damaged.

If a concern what else under hook to check??

Next is to check under dash. Idk steering column grounded? Ignition switch bad?

Can I unplug column and hot wire ignition to start car to see if that drop voltage?

Thank for advice. Jim

 

[Mattax]

I bought this 76 dart this winter. I been going overr it now that's it's nice been driving it. Looking it over( wiring) I saw nothing crazy. Like cut ,spliced wires etc. I installed a volt gauge and noticed it was a tad over 14,. As my old eyes from 3 ft saw without readers lol. I drove it the other night and headlights were going dim bright dim bright. So I check at battery and I am getting 15.6 volts.

Should I be concerned???

yes !
That can overcharge the battery (should see that on the ammeter indicating high charge rate and continued charging when it should be done). It can also burn out bulbs etc.

Next is to check under dash. Idk steering column grounded? Ignition switch bad?

No. Maybe.

Can I unplug column and hot wire ignition to start car to see if that drop voltage?

No no.

First thing is to understand how '76 is wired.
It's different than all the previous years.

Second will be to use the voltmeter to identify where the voltage drops.

 

[slapstickjim]

yes !
That can overcharge the battery (should see that on the ammeter indicating high charge rate and continued charging when it should be done). It can also burn out bulbs etc.

No. Maybe.

No no.

First thing is to understand how '76 is wired.
It's different than all the previous years.

Second will be to use the voltmeter to identify where the voltage drops.

I been using my multi meter. What do mean check where the voltage drops? Any thoughts on where to check or recheck

 

[Mattax]

A diagram of how the main circuits are wired in a '76

Wire R6 carries power from the alternator.
The alternator should be producing power at 14.2 Volts or so.

The R6 wire and the A1 wire from the battery are joined with the feeds to the key switch, headlights and fuse box.
(The wires to the ammeter carry no power to speak of. With this type of ammeter think of them like leads on your voltmeter.)

If you are measuring 15.6 V at the battery, measure the volts the VR is sensing, and the alternator is producing.
Since the regulator's connector doesn't allow easy probing at the sense terminal, go to nearest connector that can be back probed. The terminal on the ballast resistor with dark blue or dark blue striped wire is good location, and the alternator's blue field wire is another.

 

[Mattax]

What do mean check where the voltage drops?

If there is a difference in voltage readings where current is flowing, then that current is meeting resistance.

If there is resistance before the regulator then it will increase the voltage until it gets the correct reading. Lets say it senses 13 V when the alternator is producing at 14.2 V. Then the regualtor will increase current to the field unitl it senses 14.2 Volts. As a result the alternator is making power at 15.4 volts.

Before I forget, another thing to check is if the voltage is going up with rpm.
If the votlage is going up with rpm, then the second field terminal is getting grounded. This could be the insulator at the terminal broke or is missing. it could be the green field wire is pinched against the engine or body. It could be the regulator itself.

 

[Mattax]

Orange arrows show the current paths with the engine running and the battery slightly recharging.
The ignition draws 3-4 amps, the alternator's rotor (field) can draw around 4 or maybe even 6 amps on '76.

 

[slapstickjim]

I put aftermarket gauge under dash. The factory one does not do a thing. I'll be checking tomorrow. The green wire is where it all starts from alt then reg reads that and tell alt to adjust through the blueish wire to alt? And I have 4 bulkhead connectors

 

[Mattax]

Power comes from the heavy gage black wire attached to the terminal marked B or Bat.

Green goes back the regulator. The regulator connects and disconnects it from ground.

The earlier versions controlled the feed but both power up the rotor. its just controlled a little differently.
Identifying Chrysler Alternators (1960-1976)

 

[townsend]

Recommend you purchase the 1976 factory service manuals.
The electrical manual has the complete wiring diagram.
One example:

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[slapstickjim]

Thanks for advice to you guys.

What I did today, spent a few hours and sort of thinking in right direction.

All work today was under the hood.
Mattax you gave me solid guidance. Those diagrams helped big time.

Thanks

Untaped every wire under hood and inspection Them. All is good except 2 places. Which def were not the problem but I addressed them.

I tested voltage while running at alt to regulator. 15.7 at batery, 15.6 at R1 , 14.3 blue wire at alt and in-between reg . 10.7 green wire at alt and In-between reg. changed reg with 2 used one new and same numbers. Changed alt and all numbers dropped .2. Unhooked each bulkhead while running and no change in numbers. Except the one with ignition and r1 wire that shut car off.

With bulkhead off I put a jumper wire from r1 to ignition on bulkhead connector And jumped car at stater relay. Bingo number changed. 14.6 at battery, 14.4 at R1 14.24 blue wire at alt and in-between reg, 9.3 green wire at alt and in between reg. Changed reg with all ones I tested with and they number did change alil. Like .18 higher at most at each spot.

I think I'm headed to look under dash next. Look for bad ground, bad ignition switch. But not today my brain doesn't handle electrical issues well.

Am I headed in right direction???
Can I unplug the key wire and test with meter??

Thanks again jim

 

[Mattax]

Jim,
Sometimes the voltage drop can be in the grounds. Based on your tests and experimenting I don't think its a bad ground.

Maybe worth using a battery and a headlight as an example.
If the wires and connections are perfect, the voltage from the battery to the headlight stays the same all the way to the filament in the lamp.

And the ground voltage is essentially zero. on the other side of the lamp.
Current (electrons) easily flow through the circuit except for inside the headlight. That's where the voltage drops.
If you want to go to the formula its change in Voltage = Current x Resistance.

Now lets say the lamp is weak and the battery still shows 12.7 Volts

We take a couple of voltage measurements including one right at the headlight connector which shows low.

But we're not sure if the ground connections are free of resistance.
The solution is to measure voltage along the current path. Where ever the electrons meet resistance the voltage will drop.

Looks like the ground is perfect and the resistance is in the wire.
Maybe its a bad connector?

Yes it is.

 

[Mattax]

Unhooked each bulkhead while running and no change in numbers. Except the one with ignition and r1 wire that shut car off.

Engine doesn't work when the ignition is disconnected!

You've pretty well established there is resistance between the alternator and the regulator's sensing terminal.
Your experiment did not involve jumpering the grounds, so the grounds are OK.
I would check every connection along the current path from the alternator to the regulator's sense terminal.

On the inside the easiest may be to reference to ground.
Backprobe the J1 where it comes through the bulkhead.
Then backprobe the J2 to ground.
And/or measure voltage difference between the J1 and J2 on the inside of the bulkhead.
If there is a big drop between the two, then check the steering column connectors and the ignition switch.

 

[slapstickjim]

Every wire and connector is perfect in that area.
Not sure I explained clearly. Sorry. I had the bulkhead disconnected , the one that has fuse link and ignition. I hooked a bypass wire between those 2. As in I had it like ignition switch was on but the bulk head was still disconnected. Isolating everyth8ng to engine bay forward and bam voltage looked good. Reread my list did I make sense? I started by jumping relay and ran fine. So that shows to me that problem lies inside.

Looking at my number with jumper I'd say good?
I'm leaning the key switch is acting up?

 

[slapstickjim]

With bulkhead unhooked, I just put meter on j1 and j2 on firewall side. I set it for ohms then turn key on and meter would not settle. Bouncing all over the place.

Like i said had steady 14.6 when bulkhead unhooked and jumper j1 and j2. With car running and totally isolate all wiring to engine bay.

 

[Mattax]

yes I understood.
That's why I wrote what I did.

First. Disconnecting a running engine didn't prove anything. That's why I made a joke about it. How is the electricity going to get to the ignition ECU and coil if the J1 is disconnected?

Second. It seemed you did not understand why I asked you to measure the voltage at the different locations along the current path. That's why I tried to explain the technique and how one can measure voltage drop directly when there is a question about grounding.

Third. I took your information and suggested where to probe next to narrow down the location(s) of resistance. That's what I would do.

 

[Mattax]

With bulkhead unhooked, I just put meter on j1 and j2 on firewall side. I set it for ohms then turn key on and meter would not settle. Bouncing all over the place.

OK. or really not OK.
An ohm meter shouldn't be used to measure hot circuits.
Most ohmeters work using a very small electric current.
You have to disconnect the battery.
Second. The resistances we are talking about are small. Too small for most ohm meters to pick up.

Lets run the numbers and see what the resistance might be.
Assume its an original alternator and ignition. That's about 5 amps for the field circuit and 5 amps for the ignition.
V = I x R and we fill in the drop in volt and estimated current.
1.5 Volts = 10 amps x Resistance
0.15 ohms = Resistance estimated along the path.

Look at the diagrams, or make your own, and think aboutor draw out how the electrons are getting from the power source to the measurement point.

 

[slapstickjim]

Misunderstood or I did not explain sorry. In my triaI i unhooked each bulkhead yes and voltage stay at 15.7. Unhooking the one and shut car off yes.

Different trial with bulkhead unhooked I put a jumper from j1 to j2 but did not plug bulkhead in. Mimicking key turned on. Screwdriver to starter relay and all voltage number seemed to corect itself. That's the numbers I gave in second list. 14.6. Solid and steady. That's why I meant under hood seems good and bulkhead in seems to be an issue.

I did measure voltage all over the place. Under the hood. Wires have all been completely untaped unhooked and spent like an hour checking each wire for bare wires etc. I did check voltage all over the place. Nothing seemed different. Even changing alt and reg was same. I thought I was Damm thorough in my testing. Frustrated ugg sorry

You have been super helpful and I thank you.

 

[slapstickjim]

OK. or really not OK.
An ohm meter shouldn't be used to measure hot circuits.
Most ohmeters work using a very small electric current.
You have to disconnect the battery.
Second. The resistances we are talking about are small. Too small for most ohm meters to pick up.

Lets run the numbers and see what the resistance might be.
Assume its an original alternator and ignition. That's about 5 amps for the field circuit and 5 amps for the ignition.
V = I x R and we fill in the drop in volt and estimated current.
1.5 Volts = 10 amps x Resistance
0.15 ohms = Resistance estimated along the path.

Look at the diagrams, or make your own, and think aboutor draw out how the electrons are getting from the power source to the measurement point.

All bulkhead unhooked when I tested that so appsolutely no power inside

 

[slapstickjim]

My handy get a car started bypass trick. Hope that gives you visual off how I isolated the ciciut to just engine bay and had car running

 

[DartDave73]

One thing that kind of stood out to me is that you noticed that the lights were going from dim to bright back and forth. Does any other light, say the dome light, do the same thing? Or is it just the headlights? I would check the harness behind the grill and see if there are any grounds to frame on the light circuit. Those radiator support frames can get pretty rusted out if it hasn't been worked/replaced.

You also might be able to isolate the circuit in question by bridging the fuses with a voltage meter/amp gauge or a test light, and see if that points to anything.

 

[slapstickjim]

One thing that kind of stood out to me is that you noticed that the lights were going from dim to bright back and forth. Does any other light, say the dome light, do the same thing? Or is it just the headlights? I would check the harness behind the grill and see if there are any grounds to frame on the light circuit. Those radiator support frames can get pretty rusted out if it hasn't been worked/replaced.

You also might be able to isolate the circuit in question by bridging the fuses with a voltage meter/amp gauge or a test light, and see if that points to anything.

Headlights,dome lights aftermarket gauge
Ights all did same. I did check headlights and ground and all seemed OK. Like I was saying g here when I totally bypassed ignition with jumper voltage corrected itself. That's why I'm leaning is my key bad or wire in that atea? I could be way wrong of coarse.

 

[slapstickjim]

According to mattaxs last diagram the only circuit not checked yet is bulkhead to key back to bulkhead

 

[DartDave73]

JUst a quick thought, but have you checked the grounding of the voltage regulator to the body?

 

[slapstickjim]

JUst a quick thought, but have you checked the grounding of the voltage regulator to the body?

Yep 5 dif ways.

 

[DartDave73]

Headlights,dome lights aftermarket gauge
Ights all did same. I did check headlights and ground and all seemed OK. Like I was saying g here when I totally bypassed ignition with jumper voltage corrected itself. That's why I'm leaning is my key bad or wire in that atea? I could be way wrong of coarse.

Issues with the ignition switch harness in the column? They have been known to do some strange things.