help checking the wiring

[xs29bb1]

My battery is sitting at about 12.4-12.5V when the car is running, even when I rev the engine so the alternator is not doing its job.  I'd like to check the wiring some before getting the alternator checked, but I need some help on what to check and where? 

The car runs fine, (for now) but it looks like the fuel gauge is off.  (reading 3/4, should be full)

I don't really know the system, but here is what I think I know from looking at diagrams.

Green wire from alternator goes to voltage regulator
The other side of the regulator goes to the ignition resistor which goes to the coil (I'm assuming that since the car runs fine, the voltage at the coil is OK?), and also goes to Q (which I'm guessing is a firewall connection?)
From there connection J goes to the fusible link which then goes to the battery

Is that correct, and is that the path I should check?

Also, someone else mentioned on another thread (I'm moving it over here as I didn't originally put it in the right place) that I need to check to see if one of the field wires is grounded.  I can just check the voltage on either side of the regulator for this I guess.  What voltages should I be reading on each side if its working correctly?

http://www.dodgecharger.com/forum/index.php/topic,112929.0.html

Like I said, I just got the car recently and I don't really know much about it.  Any help much appreciated. 

Thanks

[Pete in NH]

Hi,

I read through both your threads and I didn't see what year car your working on. 69's and earlier get a little tricky as they have a different alternator/regulator system than later cars although they are often converted to the 1970 and up electronic system. If you are not sure what is on the car presently take a picture of both the regulator and back of the alternator and post them.

[xs29bb1]

Hi,

I read through both your threads and I didn't see what year car your working on. 69's and earlier get a little tricky as they have a different alternator/regulator system than later cars although they are often converted to the 1970 and up electronic system. If you are not sure what is on the car presently take a picture of both the regulator and back of the alternator and post them.

Thanks.  I've got a 68 and it should be 100% stock wiring setup.  The diagram I was looking at was from a '70, so mine might be a little different from that as you said.  It looks to me that the blue wire from the regulator might go right to the coil.  Also, I could only see the green alternator field wire, but that might be because there are too many plug wires in the way.  I was going to disconnect the plug wires to get a better look.

Any help appreciated!

[Pete in NH]

If you have a stock 68 system, you should have a regulator mounted up on the firewall with only two separate wires going to it both on screw terminals or push on connectors. There will be two separate connections. The green wire from the regulator goes down to a single field connection on the alternator. Is this the system you have on your car?

[xs29bb1]

If you have a stock 68 system, you should have a regulator mounted up on the firewall with only two separate wires going to it both on screw terminals or push on connectors. There will be two separate connections. The green wire from the regulator goes down to a single field connection on the alternator. Is this the system you have on your car?

Yes that's what I have.  There's a screw connection for the green wire, and a blue wire on the others side which is a push on.  I just fired up the car and read about 11.7V on each side of the regulator.  (seems low)

I believe the ballast resistor is next to the regulator on the firewall.  I measured the voltage there on each side.  (to ground)  One side is also 11.7V, and the other side is about 6.9V

[Pete in NH]

Okay, from your measurements on each side of the voltage regulator it looks like the regulator is working and trying to do its job. I suspect the alternator output stud to battery path is open somewhere. I would check the red wire side of the ammeter to battery circuit first. Ammeter stud to bulk head connector pin to battery stud on starter relay though the fusible link. From starter relay battery stud to + side of battery. My bet would be either the fusible link is open or the bulk head connector pin is burnt up.

[xs29bb1]

Okay, from your measurements on each side of the voltage regulator it looks like the regulator is working and trying to do its job. I suspect the alternator output stud to battery path is open somewhere. I would check the red wire side of the ammeter to battery circuit first. Ammeter stud to bulk head connector pin to battery stud on starter relay though the fusible link. From starter relay battery stud to + side of battery. My bet would be either the fusible link is open or the bulk head connector pin is burnt up.

Here's a pic of my connector.  As you can see, all the wiring is basically new.  Corrosion shouldn't be a problem, but I guess something is just open.  

If I ohm it out, the J connector to the fusible link to the battery is all 0 ohms.  Here's one thing I found that I'm not sure about.  The alternator has both a black and purple wire.  I believe this purple wire connects right under the J connector at the firewall? If I ohm out the purple wire at the firewall back to the alternator it's 5M ohms.  Should that be a straight connection - I don't know what the purple wire is for.  

Is it safe to simply jump the alternator to the positive battery terminal to see what it reads when running?

[Pete in NH]

Okay, so nice to see all new harnesses. But, there's still an open circuit somewhere. Yes. you can connect a wire directly from the alternator output stud to the battery as a test. If the battery voltage comes up to 13.8 to 14.4 volts or so , you will know the alternator and regulator are good but the charging circuit path is open. Use at least a #12 gauge wire and I would disconnect the negative battery cable before installing the test wire, then reconnect the negative battery cable. Then start the engine and measure the battery voltage.