Odd....did my alternator just go south on me?

[Dodge Don]

About a couple of months ago I replaced my old repro group 27 battery with a new repro group 27 battery. The old one was no longer holding a charge. Ever since my car was completed the volt meter (I had my amp meter upgraded to volts) always had the needle about 3/4 of the way to the right. I noticed that after swapping in the new battery that it dropped to about the 1/2 (center) mark...I assumed it was reading less volts because the new battery was not in need of more??

After fully charging the battery, with the key on but engine off, I noted that the volt meter read just slightly above the 1/2 way (center) of the gauge. After starting the car at idle the volt meter dropped slightly below the 1/2 way mark. When I checked the voltage at the battery while at idle I got 12.3 volts...if the alternator was working shouldn't this be somewhere in the 13.5 - 14 range?

Seems odd that the alternator would go at exactly the same time I installed a new battery. Any suggestions? As a reminder I'm using an MSD 6AL box.

In this video which was taken just before swapping batteries you can see the volt meter (amp gauge) at around 3/4 to the right at about 15 second mark in the video
http://www.youtube.com/watch?v=ZKR5ESy3IOc

In this video which was taken a few days later after swapping the batteries you can see the volt meter (amp gauge) at just under the 1/2 way center at about 29 second mark in the video
http://www.youtube.com/watch?v=VyeILKjzl70

[Pete in NH]

Don,

Thanks for the video clips, I greatly enjoyed the ride along. On your charging system issue, yes, the voltmeter should be reading somewhere between 13.4 or so to 14.5 volts. Your 1970 was the first year for the Chrysler electronic regulator and isolated field alternator. Is that the system still on the car? Try putting your new battery on a separate battery charger and See if will take a charge. If it does, and you still have the original alternator/regulator set up, disconnect the green wire at the alternator field and ground the field terminal the green wire went to. If the voltage goes up the regulator, green wire or  regulator ground is bad.  If  the voltage doesn't go up the alternator is likely bad. Good luck and let us know what you find.

[Dodge Don]

I'm using the MP Electronic Ignition distributor with an MSD 6AL box.

[Pete in NH]

Okay on the ignition system. Its not likely connected to your charging issue. I was asking about the alternator and regulator system on your car and if it was the factory original system. Up along the top of the firewall you should have a small square box with two wires coming out of it one green, one blue if it is the factory system.

[Dodge Don]

Okay on the ignition system. Its not likely connected to your charging issue. I was asking about the alternator and regulator system on your car and if it was the factory original system. Up along the top of the firewall you should have a small square box with two wires coming out of it one green, one blue if it is the factory system.

Nope.

[Pete in NH]

I guess at this point then a few pictures of the alternator, firewall area and engine compartment might help identify what type of alternator system is on your car. Once what is there can be identified I can give you some ideas on how to check it out.

[Dodge Don]

Hmmm....now you have me thinking  

When I installed the MSD 6AL box I was led to believe that I no longer needed the ballast resistor or the voltage regulator. They are both still on my firewall for appearance purposes however the wiring for both is unconnected...even though they run into the harness and look connected. I have my wiring diagram at home so I know exactly how I wired it all and how I terminated the voltage regulator and ballast resistor wiring...I'll need to look at that diagram.

Should the voltage regulator be hooked up when using an MSD box?? The MSD wiring diagram/instructions make zero mention of the voltage regulator. Maybe that is my problem?

[Pete in NH]

Don,

I think you've found your problem. You still need the voltage regulator hooked up for the alternator to work. The new ignition system really doesn't have anything to do with the voltage regulator, they are two separate systems. I bet if you reconnect the voltage regulator the way it was all will be working again with the charging system.

I don't know anything about the MSD box, so I don't know about needing the ballast resistor or not.

[Dino]

You ran that car without a voltage regulator?  You lucky man!  Unless you install an alternator with internal regulator you will need to hook up the blue and green wires from the regulator.  The ballast resistor may not be needed but check with MSD to be sure.

[Dodge Don]

I looked at my wiring diagram (how I wired it up) and I was mistaken, I did wire up the voltage regulator...it was only the ballast resistor I bypassed (which MSD suggests).

Everything was fine until I replaced the battery....immediately I saw a drop on the dash volt meter. I'm wondering if during the battery swap I disturbed the rad support ground wire to the battery negative cable.  Maybe I'm not getting a good ground.

I'll have to check that.

[Dodge Don]

Well it doesn't seem like a ground issue. I did some tests this afternoon....thoughts?

Before starting battery was at 12.7 volts. Started car and measured volts across battery terminals and got 12.3 volts. So still no charging going on.

I tested all the glove box fuses...all okay.

I tested the ground by testing the continuity with chassis.  Battery read 12.5 volts....disconnected negative cable and then tested voltage between positive battery terminal and disconnected negative cable...I got 12.5 volts.

I tested the alternator output continuity. With negative battery cable disconnected I set meter to ohms and checked continuity from alternator output stud to battery positive post....I got 0.5 ohms which I understand is good.

I tested the voltage drop through the harness to the battery by hooking up battery, putting key into run position, putting a meter probe on blue wire alternator field connection and other meter probe on battery positive post....I got a reading of 0.2volts which Iunderstand is good.

Finally I tested the alternator voltage output. Engine running around 1200 rpm...put meter probe on alternator output stud and other meter probe on chassis ground source...tried with 2 different ground sources and both times I got an alternator output of 12.21 volts.

I thought I had a spare old voltage regulator to try a swap but couldn't find it.

So it seems to me, based on the above, that I need to have my alternator replaced/rebuilt....thoughts?

Any tests I missed?

[Just 6T9 CHGR]

Don, I'd say you covered all the bases & then some....shes dead Jim...time for a replacement

[Pete in NH]

Don,

Go back to my first post in this thread. You still might have a bad regulator and the alternator is okay. You should have 12 volts on the blue field wire at the alternator. If you do remove the green wire and ground the field terminal it came off of. If the voltage across the battery comes up the regulator is bad, if it doesn't the alternator is likely bad.

[Dodge Don]

I pulled the blue and green alternator field connectors off. I then jumped a wire from the blue field terminal to the alternator output stud. I then attached a wire to the green field terminal and with engine running I grounded the wire from the green field terminal to the negative battery cable chassis ground while monitoring the volts at the battery posts. There was no change/effect. If I understand correctly this should have spiked the voltage supplied to the battery.

So unless I'm missing something I think this rules out the voltage regulator and I'll be pulling off my alternator to have it replaced.

[cdr]

that would be correct. also make sure you have voltage at the post on the alternator without the car running.

[Dodge Don]

Just installed the new alternator this morning....that was the problem. Charging around 14.4 volts steady now.

Thanks for the advice guys.

[bill440rt]

 Well that's good news.
   HAPPY NEW YEAR!!