New Voltage Regulator at 15V?

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gzig5

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I put in a new engine wiring harness and when I took the voltage regulator off the firewall to clean, I saw the potting compound was melting out. Got a new VR from NAPA and when the engine is running, I'm getting 15.05V. Seems a bit high?

On the good side, the ammeter needle is steady and in the middle. Memory says the old VR usually ran low to mid 14 volts (14.1 - 14.6) and the ammeter was always bouncing on the charge side. Voltage was definitely not as stable as the new one has it. I didn't know it had an "issue" so I didn't check it before everything was torn apart.

So, is 15V going to be OK or should I take it back for another one? Any recommendations on a good VR that works as it should, doesn't leak potting compound, and doesn't cost an arm and a leg?
 
Its a wee bit high for this time of year but see if it comes down after it warms up.
I don't know what's going on but it does seem like some of the electronic VRs are set higher than typical stock or run high for the first few minutes.
The other thing thats real important to check is for a voltage drop.
Take the voltmeter and measure the difference in voltage between the alternator output and the regulator control wire (usually blue). Could check it at the ballast resistor or the alternator - should be the same in both places. I assume this is a ground regulated alternator (regulator has the triangular plug, each alternator brush has a wire connection to the regualtor).
 
dodgeboys.net said:
the Dodge FSM and industry standard is Min=13.0 to max 14.5
Click to expand...
Need to check your books.
page 8-122 Dodge Passenger Car 1973 Chassis Service Manual
upload_2019-7-7_12-0-51.png
 
Mike69cuda said:
How good is the meter you are checking it with? Is it accurate?
Click to expand...

$400 Fluke 87 which gets professionally calibrated every twelve months. I'm pretty confident that it is reading correctly.


Mattax said:
Its a wee bit high for this time of year but see if it comes down after it warms up.
I don't know what's going on but it does seem like some of the electronic VRs are set higher than typical stock or run high for the first few minutes.
The other thing thats real important to check is for a voltage drop.
Take the voltmeter and measure the difference in voltage between the alternator output and the regulator control wire (usually blue). Could check it at the ballast resistor or the alternator - should be the same in both places. I assume this is a ground regulated alternator (regulator has the triangular plug, each alternator brush has a wire connection to the regualtor).
Click to expand...

The 15V is measured at the battery terminals. I'll poke around a couple different spots and see if there is any difference. The alternator has two field connections and the black heavy output wire. No polarity marking on the fields or in the diagram so I just connect the field wires to suit the wire length. From what I've found, field polarity should make no difference in a properly functioning system.

I'm not sure I'm comfortable running it that high so we'll see how it settle out but I may be taking the VR back for a different one to try. I'll also swap in the old one just to confirm it's behavior, but it is a gooey mess on the back side and I don't want that crap dripping down the firewall.
 
gzig5 said:
The 15V is measured at the battery terminals. I'll poke around a couple different spots and see if there is any difference. The alternator has two field connections and the black heavy output wire. No polarity marking on the fields or in the diagram so I just connect the field wires to suit the wire length. From what I've found, field polarity should make no difference in a properly functioning system.
Click to expand...
sounds good.
Correct. On the '70 up systems, the blue wire is the rotor's power source and it's voltage determines what the regulator does.
When system voltage is low, it connects the green wire to ground. When system voltage is high, it opens the connection, interupting flow which causes the magnetic field to diminish. In between IIRC it restricts the flow using a resistor.

Lets say the battery is 15 Volts above ground.
Its possible the Alternator output stud is also at 15 Volts, but the 'ignition' wire from the ballast to the alternator is at 14.3 Volts.
In which case the regulator is doing its thing correctly.

Since the drop in voltage must be between the main splice and the 'ignition' wire, this would indicate a resistance between the main splice and that wire.
When using an analog gage its easier to measure voltage drops with by measuring voltage between two points in the cirvcuit; as opposed to measuring voltage above ground. With a digital gage it still is useful for tracing because it eliminates voltage drops in the ground circuit.

Feel free to substitute 'run' for every place I wrote 'ignition.' Chrysler always called that the 'ignition 1" circuit but it's always had a branch to supply the alternator.
 
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Drawing of that example assuming the battery is charged.
upload_2019-7-7_13-52-47.png


If the battery is charging, and the battery is at the same voltage as the regulator, same deal.
upload_2019-7-7_14-0-28.png

In fact if there is no drop between the battery and the alternator during charging, it helps narrow down the locations where there is resistance to flow.
 
My Voltages are exactly as your drawing, i have not had any issues. I will run the car as it is. 15.2 and 14.6 at those 2 locations On the Alt filed wires at the Alt, i have 10vdc on the green and nothing on the blue while it is running.
 
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