Charging Problem

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1966 valiant

1966 valiant

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First I suck with electrical problems. Sorry in advance that this post is kind of all over the place, much frustration right now. Here's what started happening last night. my car 66 valiant with a 318. First I found out my battery was dead just picked up a new one and have the same problem. My volt gauge appears to be charging at about 11.5 volts. I recently had the fuel gauge rebuilt and it was working fine until now. While driving on flat road it dropped to empty and then went back up (did this twice) now it is stuck on empty again. Alternator is new. Just took a test drive and volt gauge is holding steady at about 11 or 11.5. No ammeter hooked up. No electrical was running. When I got it back in the garage tried turning the headlights on and the gauge dropped way down. No change with heater or radio. Could voltage regulator be bad. Or is it more likely a short possibly from the fuel gauge. I do have a volt meter but don't have a clue how to check things with it. Any pics of how to check would be great. But any advice would also be helpful. This sucks it's a beautiful day to cruise. Thanks in advance.
 
Well we have to make a few checks and figure it out.

First, we need to know what kind of VR you have, that is:

Do you have a factory Mopar system, or a modern "Denso" or some other swap?

Do you have an original type 69 / earlier VR or has it been converted to the 70/ later?

IF YOU have the original 69 / earlier, the VR should look something like this:

$_35.JPG


If it has been converted to the 70 / later "isolated field" it will look like this

mZxayOWFTOeuGBGuBRdKWOA.jpg


The above is the FIRST THING we need to know
 
You need some basic tools. Not just for this job, but "because."

You need a spark tester, a 12V test lamp, a multimeter, and a few (at least two) alligator "clip leads."

Assuming you have the original 69 system, we can divide

a "no charge" problem into different sections.

Might be bad alternator

Might be bad VR

Might be charging output circuit harness issues (from output of alternator to battery)

Might be field wiring issues

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So let's dig right in with some simple tests

First, get to the alternator and remove the green field wire, it simply pulls off. Take your alligator clip leads and hook the alternator field terminal to a battery source, such as the big stud on the starter relay. DO NOT use the alternator output stud. We'll get to that

Start the car and slowly bring up RPM while monitoring battery voltage. Any increase? No?

Move your voltmeter to the alternator output stud, and repeat. Any increase?

If no, the alternator is not charging

If the alternator stud voltage goes "quite high" but the battery voltage stayed low, then the circuit path from the alternator output to the battery is 'broken' that is open.

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However in the above test, IF the voltage at the battery starts to climb, this means the alternator is charging, AND the wiring from the alternator output to the battery is intact.

Now, "is it" the field wireing?

REMOVE the VR. Unhook both wires. Jumper the two wires together, and reconnect the green field wire at the alternator. Repeat, run the engine, check battery voltage. Does the voltage still start to rise?

If so, this shows that the field wiring is OK.

NOW scrape clean the VR mounting base and the firewall, and remount the VR TIGHT with star lock washers. The VR MUST be grounded. Run the engine and see if it charges. If not, replace the VR
 
Yup. Go through what I posted and report back. These are simple, easy systems to figure out, especially a "no charge" problem
 
I will be trying this. Unfortunatly running out of time right now have someplace to be. Most likely try it this evening or in the morning. Thanks for your help. I will post as soon as I get to look at it.
 
Thanks 67dart273. Got to go over the car today. Definitly voltage regulator. Couldn't have done it without you.
 
Very good. These are some of the easiest systems to troubleshoot, with no "extra stuff" in there for idiot lights, etc.
 
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