1972 Duster wiring troubleshooting

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gunsmerc

gunsmerc

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Hi all- putting together a project and having some electrical issues. The car is a slant 6 with a 4 speed overdrive manual that I have wired the safety neutral to ground. I have power to the firewall and up to the anmeter on the dash, but nothing at the fuse box and no lights, turn signals, or anything else. Am I missing a relay somewhere?

And what is a good source for a wiring diagram? I see Classic Industries sells them, but are they worthwhile???
 
Go to MyMopar and download yourself a factory service manual which is FREE. That manual and some others over there, by the way, came from the guys on HERE. Also get into the "wiring diagrams" section there and download the aftermarket 2-page diagrams, which are not as detailed, and leave out some options but can be easier to follow. We can help you wade through this.
YOU MAY HAVE the age old problem with the bulkhead connector, fuse link, ammeter circuit. READ this article and even if you don't perform this bypass or in the manner the article lays out, it at least details a good overview of "how' and "why" of this problem

The main power to the lights and fuse panel "hot" buss as well as main power to the key switch comes of the "welded splice" which is in the large BLACK ammeter wire a few inches from the ammeter, and wrapped up in the under-dash harness

You may have a couple of possibilities........One is that you may be checking voltage WHILE THERE IS NO load turned on, and getting a false reading. This means that "if that is so" the trouble could be anything in the path, Wire terminal bad leading to the fuse link, the link itself, the bulkhead connector, connections at the ammeter, the ammeter itself, or the welded splice could have failed which DOES happen. These points in red--follow along on the diagram posted--are really the main characters in problems with main power loss

Try rechecking your results with the key turned to "run" and maybe the headlights turned on. Check voltage at the path. This is actually a simple circuit.



Catalog

From that article is this simplified diagram of the main power distribution:

amp-ga18.jpg
 
Last edited:
gunsmerc said:
And what is a good source for a wiring diagram?
Click to expand...
The factory shop manual for your year. For the wiring in '72, whether its a Dodge, Plymouth Service Manual doesn't really matter.
They are by far the best to refer to.
'72 may also have some cable and wire routing drawings.

gunsmerc said:
Am I missing a relay somewhere?
Click to expand...
No.
gunsmerc said:
nothing at the fuse box and no lights, turn signals, or anything else.
Click to expand...
Is the other side of the ammeter connected to the main splice?

The ammeter is a part of the battery power feed. There are two different colors used to insure the ammeter reads the correct direction.

When the wires are connected, black is hot, just like the red is hot.
The black wire is connected to the MAIN JUNCTION. This is a WELDED SPLICE.

Everything connected to the welded splice is hot.

With the key off, there should still be power at the fuses for the dome light, brake lights, tailights. There should also be power for the headlights (no fuse - circuit breaker inside the headlight switch).
If none of them have power, then the break is in the circuitry before where they all join. Right?
upload_2022-1-1_13-31-34.png
 
One more big clue and caution.
The ammeter shows current flowing in or out of the battery.
Its another useful tool.
Its calibrated roughly 40 amps to 40 amps.
Anything close to 40 amps either way is DANGER DANGER
 
I should have mentioned the easiest first check for connections to the mainsplice is using a voltmeter at the alternator's output stud.
 
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