Help Diagnosing Electical Issues

[Cudajason]

I have been working on my cooling issue, long thread over in the engine section and an electrical issue seems to have popped up.  There has been some great suggestions on my cooling thread, but wanted to get other insight as well.

So after installing new electric fans, i noted the voltage dropping to 8volts on the volt gauge once the fans kick on.

I suspected the Alternator was not able to keep up.  however, I removed the electrical fans and used the clutch fan, and after a short drive the gage dropped back to 8.

At idle the alt put out a little more than 12 volts, never more even at higher RPMs.

Last year I smoked the battery due to a wiring issue on the VR.  I fixed the wiring and added a new AGM Battery.  That was recently tested and seems to be OK.

I have done the Mad Electrical Amp Meter bypass.

The ignition box is new last year.  I did not notice any electrical issues the first time out this summer,
This all started after the fan install, but continued with the fans disconnected.  Could it be an issue with the relay I install for the fans?

Current suggestions are the verify all the grounds and connections are good and do not have any resistance.

Ground the Feild wire to see what the output is.  Does it mater which field wire gores where?

Any help would be appreciated.

[jimynick]

Jas, the one thing I can comment on is the alternator output. 12 volts just won't cut it.  I typically look for an output voltage of 14 or a wee bit better. Do you have another alternator?

[JonH]

Will a 50 year old alternator charge an AGM battery correctly? Also you should be seeing 13.5 volts or more when the car is running....not much help I know

[Skdmark]

If you are adding additional electrical items like fans, then get a Powermaster alternator.
I installed one 2 years ago when I added a Holley Sniper.

[MoparLeo]

For the battery to be " ok" it needs to be fully charged. Do not try to charge a battery with your cars alternator. It is not designed to do that. You can damage your alternator.
Battery chargers are designed to do that. The battery than needs to be load tested and pass.
After surface charge is taken off it should load @50% of CCA rating to no less than 9.7 volts. If it does, no good.
Naturally recheck all electrical connections and grounds. Not just a jiggle test.

[Chryco Psycho]

Your Alt is dead , don't waste $$ on Powermaster junk either , I have seen them last less than 1 day .
With a charged battery you should have 14.2 v minimum.
no it doesn't matter which wire goes where on the Alt it is just a closed circuit in & out although usuall one wires is a bit shorter & only reaches the top terminal easily .

[dodj]

If I remember right, leave the blue wire on, ground the other. Should prove out whether your alt CAN put out over 12v if commanded to. If it goes over 14v you have a resistance problem, re wiring or VR. If it doesn't, you have an alt problem. Dropping quickly to 8v without significant load may indicate your battery has been killed though...

FYI...My mopar alt charges at 14.1-14.3 at idle after starting and drops to about 13.6-13.8 after a bit.

[Bullitt-]

 Ground the terminal that green wire goes to to bypass the voltage regulator

here's a decent step by step video https://youtu.be/uxVwuF5SI90?t=175

[Jay Bee]

Just bringing over Brad's offer with his link.

Same price? I've had them on my cars for over 10 years now with no issues? These do actually charge at idle, unlike mopar alternators sometime struggle doing this?
I also have a spare I could lend you to try if you want? I have the same alternator on both the Challenger and the Javelin, and one spare.
https://www.qualitypowerauto.com/catalog.php?item=557

[Cudajason]

Well I am man enough to admit when I am wrong. Thanks to @dodj for pushing me to test and evaluate the problem, instead of just replacing shit.

@Bullitt- . That video was a great help.

I checked the voltage at the field wire 11.4, both read the same voltage, slightly lower the the charging amount.

I grounded one, nothing. Grounded the second, bam, alt is reading 16.xx volts.

So it looks like my VR is bad...or a bad wire / connection somewhere.

[Cudajason]

New VR installed today...first fire up and the volt meter was 15 pluss.

Checked the alt with the multimeter and it read 15.67 volts

So time for a test-drive!!!!!

Or is that too high?!?!?

[7212Mopar]

  Still have plan to replace the stock alternator to accommodate the draw from the electric fans?

[Bullitt-]

  I believe that 15+volts is to high. I would charge the battery fully with a battery charger and if the situation continues suspect the new VR is bad or the Blue wire that the VR reads the need has poor connections or degraded wires.

[Cudajason]

  I believe that 15+volts is to high. I would charge the battery fully with a battery charger and if the situation continues suspect the new VR is bad or the Blue wire that the VR reads the need has poor connections or degraded wires.

Never mind. I just put the old VR back on just to see if the new one was bad. With the old one, reading over 16volts!!!!

Maybe to old one is bad???

I will pit the new one back on and check the wires.  The wires are all new as I redid that part of the harness last year.

[Bullitt-]

   Do you know how to perform a voltage drop test?  I have been searching for a relatable video but most are bench tests with minimal losses. This one focuses on the battery terminal but can be conducted between any two points in a circuit for instance you could put one lead on the + battery terminal and the other to the VR connector with the Blue wire (with ignition in run position) to see how much loss there is total. I believe .5V or less is acceptable. If it's higher you can break it down into smaller segments to see where the problem lies.

  https://youtu.be/3-9oZuX6-Pg