Seriously another alternator question.

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Syleng1

Syleng1

Karma is real and Life is short...
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1966 Barracuda S 273-4bbl auto car
All harnesses were replaced during 3 year rest. Previous VR / Alt combo was 72 and newer style cobbled together by previous owner. Now the car is all Factory style no mods. Quality harness manufacture was used.
All grounds verified and checked. Battery to block, block to firewall, firewall to battery.
Alternator was rebuilt 66 Style from a reputable local shop known for restoring automotive electronics. Stator was replaced during rebuilding *possible issue* please read on. Tested good on tester at his shop. 68amps output max.
Voltage regulator(s) have been from Napa, bobozone and online- I even tried factory points style I cleaned and adjusted per FSM. Final VR unit is from classic industries and is electronic insides but exterior looks factory 66’ style.
All electrical connections have been checked and verified for operation and connection.
Battery voltage at voltage regulator from key matched.
My alternator is charging in the 15v+ range at idle. I have zero add-ons. No speakers, no amps, no electric fuel pumps- this car is as close to factory as possible.

Now I’ve done some reading in previous posts about alternator issues and I read about stator replacements being wound with larger wiring to make one fit all situation from rebuilders. The factory style VR cannot handle the additional load and over charges.

Has anyone figure out a work around for this besides go to a factory stator? As my rebuilder stated he had to change mine due to a short in the windings from the coating cracking. I believe this is my issue. The stator is pulling too much and causing my VR to go full charge. I was wondering about a resistor to compensate but at the risk of making my self look silly…. Because there are way more smarter people on here than I.
I am asking not telling - lol!
Thanks in advance- Syleng1
 
The voltage regulator needs to be grounded, it will go full charge with no ground. I would add a ground wire to one of the mounting bolts to start with. Don’t sand off the paint under it to do this. The factory never did it and they build millions of cars. And it just causes more problems later.

Do you have a ground wire from the engine to the firewall like factory had?
 
I have posted on this problem hundreds of times. Here we go in no particular order, except no1

1...VOLTAGE DROP IN THE VR IGN / FIELD CIRCUIT
2...Voltage drop in the VR ground circuit
3...VR that is out of spec for voltage. If it's a solid state replacement, this is rare
4...Bad battery. This is somewhat rare. I believe sulfation can cause this

1....VOLTAGE drop in the VR ign/ field circuit: This is easy to check for and VERY popular as a cause Get a multimeter. Turn ignition switch to "run" with engine stopped. Hook one probe "as close as you can get" to the VR IGN terminal or to the "key side" of the ballast resistor. Stab the other probe directly into the battery POS post. You are hoping to read very little, the less the better. Over .3V (3/10 of one volt) or more start looking. The original path is battery.....starter relay "big stud".....fuse link.....through BULKHEAD CONNECTOR on big red.....to AMMETER....through AMMETER....out on big black to WELDED SPLICE....branch off..... to IGNITION SWITCH CONNECTOR.....through IGNITION SWITCH....back out IGNITION SWITCH CONNECTOR....out on dark blue....back out through BULKHEAD CONNECTOR........to underhood loads, branch off to feed ballast resistor, VR IGN terminal, etc.

WHATEVER YOU READ in this test is ADDED to the normal VR set point, AKA if the VR is correct at nominal 14V, and you measure 1.2V in this test, the battery WILL RUN at 14+1.2= 15.2V

This problem can be caused by ANY terminal or connection in that path. The bulkhead connector, the ignition switch connector terminals, or right in the switch contacts. One way around this is to electrically break the dark blue "ignition run" (IGN1) wire, trigger a relay with the "key" end and feed the engine bay end with the output of the relay. Feed power to the contacts from such as the starter relay "big stud."

ALSO voltage regulators are temp sensitive and temp compensated. Do this test with engine warm

2...CHECKING for V drop in VR ground circuit. Run engine at RPM to simulate low/ medium cruise RPM. Test first with all accessories off, and again with lights, heater, etc powered on.

Stab one probe direct into the top of the NEG battery post. Stab the other into the mounting flange of the VR. As in the first test, the lower the reading the better, zero is perfect. If you read more than just a 10th or so, you need to improve battery--to--body grounding.

I like to use about a 1 foot "starter" (eyelet to eyelet) cable used by Ford. Bolt one end to the rear of the pass side head, the other to the body. The master cylinder mount studs work pretty good
 
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Just to add to the confusion; somewhere between 1972 and 1976 the field current changed from 2.5 amps to ~ 5 amps. Your alternator was probably rated 30 to 35 amps. To put 68 amps thru the firewall terminals when the battery is about dead is a real bad idea. Adding a 'bypass wire' from the alternator stud to the starter relay big stud will help/cure that. Use a # 12 wire with a # 16 fusible link. Your ammeter will read about half current.

This won't cure the 15v at idle problem. Look for a poor connection. See Dart 273 above.
 
Just tossing this out there...

What size is your crank pulley?

Getting full charging voltage (yes it is a bit too high) at idle is unusual.

If crank pulley is larger than stock or the alt pulley is smaller than stock could cause the alternator to spin faster and charge better at idle. still not the cure for the voltage being high
 
Syleng1 said:
My alternator is charging in the 15v+ range at idle. I have zero add-ons. No speakers, no amps, no electric fuel pumps- this car is as close to factory as possible.
Click to expand...
Look for voltage drop and downstream as Del suggested. Then with the engine running do it from the alt out which is your power source with the engine running.
Note the ammeter readings when you are doing this. There will be more voltage drop with more current.

The book shows the acceptable system Voltage range at various temperatures.

Syleng1 said:
Now I’ve done some reading in previous posts about alternator issues and I read about stator replacements being wound with larger wiring to make one fit all situation from rebuilders. The factory style VR cannot handle the additional load and over charges.
Click to expand...
The rotor creates the field. The stator reacts to it.
The current draw through the regulator is the field circuit.
If you want to measure the rotors resistance, measure slip ring to slip ring. The carbon brushes will mess up the reading.
 
Here's why its imprtant to note the battery charging or not.

Engine running and Battery getting charged.
Orange arrows represent current flow from the alternator.
upload_2022-6-29_16-57-24.png

The alternator is producing voltage higher than the battery.
The amount of current that flows depends on the downstream needs.
In the illustration above, the battery is drawing about 15 amps and the ignition and field about 6 amps.

If the voltage difference between the alternator output terminal and the battery positive was zero, then there is no resistance between those two locations. In reality, with 20 to 25 amps going through the bulkhead connection, then 15 or so amps through the ammeter connections, the bulkhead, the fusible link, and the relay junction, a little voltage drop is expected.

Once the battery is charged, then only 3 to 6 amps is flowing through the alternator output wire.
The voltage drop between the alternator batt and the battery positive will be less than measured when the battery charging. The resistance hasn't changed, its only the amps through the resistance that changed.
upload_2022-6-29_17-11-9.png


Follow?
 
Mattax said:
Here's why its imprtant to note the battery charging or not.

Engine running and Battery getting charged.
Orange arrows represent current flow from the alternator.
View attachment 1715949261
The alternator is producing voltage higher than the battery.
The amount of current that flows depends on the downstream needs.
In the illustration above, the battery is drawing about 15 amps and the ignition and field about 6 amps.

If the voltage difference between the alternator output terminal and the battery positive was zero, then there is no resistance between those two locations. In reality, with 20 to 25 amps going through the bulkhead connection, then 15 or so amps through the ammeter connections, the bulkhead, the fusible link, and the relay junction, a little voltage drop is expected.

Once the battery is charged, then only 3 to 6 amps is flowing through the alternator output wire.
The voltage drop between the alternator batt and the battery positive will be less than measured when the battery charging. The resistance hasn't changed, its only the amps through the resistance that changed.
View attachment 1715949269

Follow?
Click to expand...

Yes I follow. I will review and advise.
 
Dana67Dart said:
Just tossing this out there...

What size is your crank pulley?

Getting full charging voltage (yes it is a bit too high) at idle is unusual.

If crank pulley is larger than stock or the alt pulley is smaller than stock could cause the alternator to spin faster and charge better at idle. still not the cure for the voltage being high
Click to expand...
All stock. Pulley wise. Diameter of alternator pulley is possibly a tad larger as he installed a new pulley since mine would not clean up on a lathe. The “V” was too damaged and he was afraid I would chew belts. But a larger pulley would slow down the alt .
 
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67dart273-

so I finally got around to going over all the info you sent. Thank you again for that. It was helpful as even thought it was all “brand new” and “installed properly.” I learned a few more things from your post.

What I finally realized was after starting and checking voltage - I really needed to just drive the damn thing. All my voltage drops were either spot on or just over what you suggested was a good number to shoot for.

After driving a bit and rechecking (10miles) I found out my voltage settled back down. Maybe it’s the solid state VR for 66’ or maybe my system loves to charge quickly as after a 10min trip around the neighborhood it settled back to 14.2v at high idle tested at the battery. I let the car sit a few and retested battery and it was at 13.5v with my DVOM. The battery is 1 year old and sat a lot charging so some build up on the plates I’m assuming.

Anyhow it is running spectacularly on this beautiful 4th of July.

thanks to everyone who jumped in with suggestions. Enjoy your day today- our forefathers worked hard for us!
Syleng1
 
It could be just temperature. Sounds like you are making good progress
 
Syleng1 said:
I let the car sit a few and retested battery and it was at 13.5v with my DVOM. The battery is 1 year old and sat a lot charging so some build up on the plates I’m assuming.
Click to expand...
Surface charge.
Put a load on it, dome light, parking lights, headlights, pick one and watch what happens. it should settle to the true charge voltage in a minute
 
My amp gauge almost always reads high (but not pegged) after initial start.
I always assumed that the high load from the starter and cold state of the VR combined to cause a higher initial output. It always settles down once warm.
 
Yes, basically.
When a low battery is hooked to a charger, controlling the voltage provides a level of control over the charging rate.

Low battery (75% charged) provided power at 13.4 Volts. rate of charge 3.3 amps
upload_2022-7-4_15-16-26.png


Same battery now charged up provide power at 13.3 V. Rate of charge Zero amps
upload_2022-7-4_15-18-49.png

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A low, but not dead, battery provided power at 14.2 Volts. Charge rate about 30 amps.
upload_2018-12-24_11-37-33-png.png
upload_2018-12-24_11-37-58-png.png


Same battery, with the charger turned down so the supply voltage was 13.3 V. Result is battery only draws 8 to 10 amps.
upload_2018-12-24_11-40-35-png.png
upload_2018-12-24_11-41-26-png.png



The regulator temperature can make a difference on the system voltage and therefore the draw of the battery and other items.
However the biggest reason for high charging current right after start is the battery is low.
 
^^This is a pretty good write up but one caveat, and that is "be careful" when making comparisons because those old chargers ARE NOT voltage regulated. You said you "adjusted the output" which is a key phrase here. Otherwise, just leaving the charger connected at the higher setting would result in overly high system voltage AND overly high charge rate AS THE BATTERY comes up in charge.

This is a dramatic and key departure from an auto system, where the system is VOLTAGE regulated.

"In theory" you could build a '"test fixture" using an alternator and regulator, and use a 100A+ alternator to charge the smallest "minibike" battery you can get your hands on, and the lash up would in theory, NOT damage the battery BECAUSE it is voltage regulated.

I basically agree, tho...........the main reasons for high charge rates after a cold start is that the battery is simply down.
 
Before alternators, generator regulators often had over current cutout or regulation. It was a normally ON relay, with both coil and contacts in series with output. When current reached max design limit, contacts would open, hence current regulation.

Generators needed current regulation, because rotor carried current, and it was conducted thru commutator and brushes. In an alternator, output current is in stator, with lesser control current in rotor via slip rings. The stator has greater heat dissipation due to large radius, surface area an open frame design. Electrically the system impedance, and mechanical design, current limit, hence active current limit left out of regulator design. Things like rotor and stator impedance, with turns and wire diameter, diode rating, pulley diameters, and chassis wiring set upper current limit for most cases.
 
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^^I'm old enough I've had a few vehicles with generators. VERY happy to "see them go." I have some older outboards with "optional" generators. "Generally," (LOLOL) I remove them. Not really needed just to go for a boat ride

Generator regulators "mostly" have 3 relays.......the voltage regulator, the current limiter, and the "cutout" which (is supposed to) isolate the generator from the battery when output is low or not running. If not the generator will become a motor

Generators must be "flashed" or polarized as to polarity, and therefore any generator can be used on either polarity when properly polarized, BUT many OEM regulators are polarity sensitive, because of the construction and material of the regulator contacts. Many aftermarket regulators were made to work on either polarity, so as to reduce stock and unique part numbers

Generator regulators MUST be matched as to amperage because (as Dave said above) the VR limits the CURRENT output of a generator, therefore protects the generator from burning up because of too much output.

"Just like" the Mopar early and late alternators, generator field circuits come in 2 types, called "A" and "B." I no longer remember which is which. One, the field gets power from the armature (output) and the VR controls the ground leg. The other, the VR supplies field power from the BATT

I realize generators "were all we had" but they could REALLY be a PITA

THE ONLY ADVANTAGE I know of a generator, is that "in theory" a car with a dead battery could be "push started" with a generator. Of course most cars cannot be push started, anyhow.....................
 
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