Steady 11.66 volts at battery... Need some help.

[James Romano]

As stated. I bring her up to a good cruise rpm... Maybe 11.80...almost 12.

Alternator rebuilt by NAPA... I test at the alternator field...same as battery. Engine to firewall ground is good.

Took off the VR and cleaned the terminals. Same readings

I did a lot of reading and found this from about 9 years ago... BUT didn't perform it as I'm not 100 percent this will find my problem. What does he mean by the output stud to test the alternator?

QUICK TEST

For a few quick tests of your charging system, simply buy a meter -- you need one anyway-- and with the engine warm, the battery "normalized" (ammeter centered after some running) and the engine at an RPM to simulate "low to medium cruise" then measure across the battery terminals. What you ideally want is more than 13.5, perfect is 13.8-14, or high end about 14.5. Higher or lower is cause for concern

If this is low, no charge, pull the field wire off at the alternator, and install a clip lead from the output stud on the alternator to the field terminal on the alternator. You should hear the alternator "grunt" and with the engine GENTLY brought up a little in RPM, the battery voltage should start to climb. Be careful not to ref the RPM too much, and monitor battery voltage. Do not rev enough to bring voltage over 15, 15.5.

If you get no output, check the voltage at the alternator stud. Should be close to battery. If you have battery voltage at the stud, but no charging voltage increase, you have something wrong in the alternator

If the voltage at the output stud is low, much lower than battery, you have a wiring problem in the charging/ output circuit, either the ammeter or the bulkhead connector is your no 1 suspects

If this test DOES show a marked voltage increase, you have either a wiring problem in the regulator/ field circuit or a bad regulator.

To check for that, unhook the wires from the regulator, and connect them with a clip lead, reconnect the field wire at the alternator. As above, the alternator should output "full tilt," and be careful of the RPM

If this test shows a charging increase, you need a regulator.



I'm wondering if the Alternator is bad and all they did was clean and paint it?

I'd like to jump into more checks... If anyone has good advice on this issue

Thanks

 

[cbarge]

What does he mean by the output stud to test the alternator?

It is the stud with black wire at 7/16's nut back of alternator.

 

[James Romano]

Mine has a red and a brown. The red is the stud with nut and the brown is a tinner wire with wire terminal

 

[cbarge]

If you are running the old electro-mechanical voltage regulator---get rid of it!
Go to Autozone and plug n play the this electronic regulator
VR706.

I fixed a half dozen old Mopars with this and they are still running around ....

 

[cbarge]

Mine has a red and a brown. The red is the stud with nut and the brown is a tinner wire with wire terminal

OK Some cars are red,others are black.
Main thing is test output att the stud regardless of wire color

 

[Davea Lux]

A lot of today's rebuilt alternators are a POS because all some rebuilders do is replace the part that failed and clean up the case. Napa should have a testing machine on site to evaluate you unit. Dollar to a donut yours has a bad diode. If you have battery voltage at the output stud the circuit to the battery is ok. If you ran the test lead from the battery to the field stud and still got nothing your alternator is bad.

Dave

 

[James Romano]

OK Some cars are red,others are black.
Main thing is test output att the stud regardless of wire color

Output is battery voltage.

 

[James Romano]

A lot of today's rebuilt alternators are a POS because all some rebuilders do is replace the part that failed and clean up the case. Napa should have a testing machine on site to evaluate you unit. Dollar to a donut yours has a bad diode. If you have battery voltage at the output stud the circuit to the battery is ok. If you ran the test lead from the battery to the field stud and still got nothing your alternator is bad.

Dave

I think you're right on this. I'll do the test lead and see what I get.

I'm assuming run the lead from the output stud to the positive side of the batter right? Would make sense

 

[mrfury68]

I don't trust parts store alternators or starters anymore. Is there an"old school" auto electric shop in your area that rebuilds alternators, generators and starters? If there is that is the way to go. You take your part in, they test it and tell you what it will be to rebuild it. Chances are you are talking to the guy who will rebuild it. Also agree on the voltage regulator. If it is the original breaker point type, replace it with a new solid state unit. You can find ones that look just like the OE type. Good luck.

 

[HWYCRZR]

Here is a link from @cbarge if you want to keep the original looking VR. If that’s what you need.
I did the same.
1968 Newport charging

 

[Big_John]

The test above is almost exactly how the factory procedure goes. I'd turn the headlights on though to give a load to the system.

One question... I'm assuming you are checking the battery voltage with a good multimeter at the battery, but if you have another to double check it, that might save you some screwing around. Or you could charge the battery... Which you should check first anyway. You should have 12.6 volts on a good, charged battery with nothing hooked up.

 

[Big_John]

I think you're right on this. I'll do the test lead and see what I get.

I'm assuming run the lead from the output stud to the positive side of the batter right? Would make sense

No... To do the test, the lead has to go to the field connection on the alternator. Output stud wire stays hooked up, field connection unhooked.

What this does is eliminate the VR out of the loop and "tells" the alternator to fully charge.

Again, check charged battery voltage before you do anything.

 

[James Romano]

I don't trust parts store alternators or starters anymore. Is there an"old school" auto electric shop in your area that rebuilds alternators, generators and starters? If there is that is the way to go. You take your part in, they test it and tell you what it will be to rebuild it. Chances are you are talking to the guy who will rebuild it. Also agree on the voltage regulator. If it is the original breaker point type, replace it with a new solid state unit. You can find ones that look just like the OE type. Good luck.

The guy at my local NAPA is like that, old school... So I'm going to bring it back and have it checked again. I don't think it was probably rebuilt.

 

[James Romano]

here's a favor to ask... can someone take a reading from their alternator output and tell me what you get at idle. If you have less than what I have.. I'm going to say it's my alternator. I know this sounds like a but of a shotgun troubleshooting, but if all else works on my system (which I really think it does) then I should have what you have... which I'm going to say is around 13+ volts. I already called NAPA and they said to bring it back in for another look.

I've been reading all kinds of good stuff the past few hours... brain is swelling... lol.

 

[The Goose]

I read somewhere that if the bulb in your BRAKE warning light burns out the circuit will not let you charge the battery no matter what you try. Some kind of factory fail safe to force you to attend to the brakes. Just throwing that out there and Mr Dave can probably confirm or deny this as fact. It’s never happened to me I just read it and filed it away as a place to troubleshoot charging issues.

Good luck I hate electrical problems.

 

[James Romano]

I read somewhere that if the bulb in your BRAKE warning light burns out the circuit will not let you charge the battery no matter what you try. Some kind of factory fail safe to force you to attend to the brakes. Just throwing that out there and Mr Dave can probably confirm or deny this as fact. It’s never happened to me I just read it and filed it away as a place to troubleshoot charging issues.

Good luck I hate electrical problems.

Hey...it's worth a shot... that's an easy one to check. Mine is burned out... wouldn't that be nuts! LOL!

 

[Big_John]

I read somewhere that if the bulb in your BRAKE warning light burns out the circuit will not let you charge the battery no matter what you try. Some kind of factory fail safe to force you to attend to the brakes. Just throwing that out there and Mr Dave can probably confirm or deny this as fact. It’s never happened to me I just read it and filed it away as a place to troubleshoot charging issues.

Good luck I hate electrical problems.

Uhh... No. Separate circuit

 

[The Goose]

I’ll find the article. I know it sounds crazy but it came from a source I trust.

 

[Xenon]

12v Auto battery depending on AGE and CYCLE should have 11.9 to 12.6 voltage output..
This is measure directly from battery while DISCONNECTED....

Alternator for these cars should be 13.8 to 14.2 voltage output..
This can be checked at the battery connections while connected to battery...

 

[Big_John]

I’ll find the article. I know it sounds crazy but it came from a source I trust.

I'd stop trusting that source.

 

[Davea Lux]

The other thing you would want to check, does your alternator have one or two field terminals? The alternators with the two lead setup need to have one of the field terminals hooked to ground, does not matter which one. Most of the rebuilts these days are the two wire variety and if you have a '69 or older car it would have came from the factory with a single wire to the field. That will work with the two wire field setup as long as you ground one terminal.

Dave