Doesn't make sense, FLD wire 11.5v

[mpro69rr]

Hey Guys,

Having a little overcharging problem, 69 RR 383 4 speed, all new wiring for the whole car with the MAD wiring. At idle I get 14.4v to 14.5v on Dakota Digital gauges (matches volt meter at battery), when revved to 4000rpm I get 14.9v to 15v. Also I had a 95amp powermaster alt (duel field with one FLD grounded to alt case) but that went up 16v at 5000rpm so I switched to my current alt (single field). not sure of the amp. Below are the tests I did, all while running:

1. Battery - to VR IGN 14.5v, same as battery
2. Battery - to unconnected from alt, FLD wire 11.5v
3. Battery - to stud on alt 14.5v
4, Battery - 12.4v to 12.5v
5. Ground at VR is good

Everything seems to check out except why only 11.5v at the FLD wire? I also unplugged the FLD wire and the battery did not charge. I have a feeling, while driving, if it goes to 5000rpm it will go over 15v. Why the increase in voltage while going up in RPM? I had another VR I tried and same thing. I finally found a VR with a volt set at 14.5v so that should be here next week. Will this solve my problem?

230-10001 Mopar Chrysler Dodge Voltage Regulator Electronic Solid State

230-10001 Mopar Voltage Regulator Electronic Solid State and Correct Restoration Look. 12VOLT SET. Used On 1960-1969 Plymouth, Dodge & Chryslers. Part Numbers CR6000, ACR6006CHRYSLER MOTORS1889960, 2095700, 2098300, 3000074, CH-524, CH-531J&N ELECTRICAL PRODUCTS230-10001, 230-10006, 231-10000OEM...

gommarts.com

 

[65CopCar]

I'm confused what you mean by unconnected field wire. Can you explain that a little better?

Is this a dual or single field connector alternator?

In general, overvoltage conditions occur due to low feedback voltage. This is usually caused by a faulty ground but can also be caused by a poor connection on the hot side. Of course can be the voltage regulator. If you had a variable DC voltage supply you could test the regulator and see what voltage it controls to.

An alternator is a 3 phase synchronous generator (or motor if you want to run it on 3 phase) with a full wave rectifier on the output. I forget how many poles it has, but my recollection is 12 or 14, but could be a little off. Voltage is controlled by varying field strength which is basically field current. At low rpms, even with a full field the alternator can't put out full DC voltage. Therefore perfectly normal for volts to be a little lower at idle. There is a lot more going on with the internal magnetics, AC voltage frequency and voltages that define DC output voltage levels at lower rpms. Smarter people than me can talk on that subject. But that is why it is imperative that the voltage regulator get a correct feedback signal in order to provide proper DC voltage output.

One time on my 1985 Charger I blew the fusible link. Lost feedback to the voltage regulator. Alternator was unload and at full field. Output was about 120 volts! Lit up my drop light.

 

[65CopCar]

And this is why voltage is lower at lower rpms. Until you get to the point where the alternator is being controlled by the regulator, the DC voltage output will be lower than rated voltage. One of the inputs for voltage getting generated on the AC side is rpms.

 

[mpro69rr]

I'm confused what you mean by unconnected field wire. Can you explain that a little better?

Is this a dual or single field connector alternator?

In general, overvoltage conditions occur due to low feedback voltage. This is usually caused by a faulty ground but can also be caused by a poor connection on the hot side. Of course can be the voltage regulator. If you had a variable DC voltage supply you could test the regulator and see what voltage it controls to.

An alternator is a 3 phase synchronous generator (or motor if you want to run it on 3 phase) with a full wave rectifier on the output. I forget how many poles it has, but my recollection is 12 or 14, but could be a little off. Voltage is controlled by varying field strength which is basically field current. At low rpms, even with a full field the alternator can't put out full DC voltage. Therefore perfectly normal for volts to be a little lower at idle. There is a lot more going on with the internal magnetics, AC voltage frequency and voltages that define DC output voltage levels at lower rpms. Smarter people than me can talk on that subject. But that is why it is imperative that the voltage regulator get a correct feedback signal in order to provide proper DC voltage output.

One time on my 1985 Charger I blew the fusible link. Lost feedback to the voltage regulator. Alternator was unload and at full field. Output was about 120 volts! Lit up my drop light.

Sorry, I meant I tested the FLD wire while it was disconnected from the alt, the output of it. Its a single field alt.
Thanks for the info, I have a new VR coming next week. I did tested it with another VR but who knows could be something wrong with that one.

 

[mpro69rr]

And this is why voltage is lower at lower rpms. Until you get to the point where the alternator is being controlled by the regulator, the DC voltage output will be lower than rated voltage. One of the inputs for voltage getting generated on the AC side is rpms.

View attachment 1716740

Yikes, that is beyond my knowledge of electrical, I have no experience, lol. What did you mean by get to the point where the alternator is being controlled by the regulator, when does the VR control the alt?

 

[BeepBeepRR]

https://www.powermastermotorsports.com/alt11_ch_oe.pdf

 

[mpro69rr]

https://www.powermastermotorsports.com/alt11_ch_oe.pdf

Thanks, but I took the powermaster off and I now have a 1 FLD alternator with black box VR. I did, however, order an electronic VR and I will put the powermaster alt back on if the VR I ordered does not keep the voltage to 14.5. I wil wire it just like your diagram, which I have.