Dash Power Feed Confusion

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Holden Customs

Holden Customs

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Hello members, I am having some trouble getting some wiring sorted out on the car, mainly where the gauge cluster gets power from and where my alternator lead plugs in. There is a harness connection at the firewall with a red wire and 2 black wires, heavier gauge, shown below.

20200803_120514.jpg


The red wire connects to the red terminal of the gauge cluster and it gets 12v from the battery. The 2 black wires form 1 wire once inside and run to the other peg (ground I assumed) of the gauge cluster. These seemed like they were once run to the alternator for some reason but I figured that couldn't be right as it would have +12v when the engine is running. I cant seem to find any other connection that exists that would make sense. Shouldnt the 2 brown wires from the alternator run back to battery? And should the black wires comming from the gauge cluster run to battery neg. ?? Here is a picture of my gauge cluster backing aswell. Any help is appreciated.

20200803_120611.jpg
 
You are a prime example........and I'm NOT making fun here........of someone who needs wiring diagrams and a service manual. You can download them FREE at MyMopar and some of the guys right here put some of them there

The big black wires ARE NOT GROUND An ammeter is a SERIES device, it measures current by being IN LINE or IN SERIES between the source and the load. The general functional path is battery....starter relay "big stud" ---fuse link---BIG RED wire----through bulkhead connector----to ammeter---through ammeter---out ammeter on BIG BLACK and a few inches from there is a BIG FACTORY WELDED SPLICE which branches off and feeds ignition switch, the fuse panel "hot buss" and the headlights switch. NONE OF THIS is fused

From that splice also is a BIG BLACK which feeds back out through the bulkhead connector to the alternator output

All this is hot at all times and IS NOT fused except for the fuse link which is darn poor protection

Please read this article: Even if you don't do this modification, this article gives insight into the wiring and problems that occur

Catalog

In that article is a simplified diagram of the main power distro in these vehicles as I described above:

amp-ga18.jpg
 
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Also we need to know WHAT IN THE HECK you are working on, year make and model. And whether it is factory stock wiring, been hacked up, or partially or fully rewired at some point "if you know."

THE PHOTO of the red wire suggests you MAY have what is known as "police fleet taxi" wiring which was optional and used with heavy duty 65A alternators. This took the big ammeter wires OUT OF the bulkhead connector and ran them through grommets in the firewall, although I don't remember there being multiple wires through one grommet as you are showing
 
By the way the yellow coming off the ammeter in one photo is NOT factory and is bad practice. Any power should be pulled off through a fuse or breaker, and should be on the "black" side of the ammeter, not the red
 
Heck if you hadn't included a picture of the back of the ammeter it could be a '76, which is different than all of the others.
 
67Dart273 said:
THE PHOTO of the red wire suggests you MAY have what is known as "police fleet taxi" wiring which was optional and used with heavy duty 65A alternators.
Click to expand...
It sure looks like that's a possibility!

@Holden Customs
Exact model and year will be important, especially for this. A) it's not an option we see alot. (B) There are several variations on how this was done.

You gave us another clue when you wrote that the black wires are spliced together and connect to the ammeter's other post.

This what we are seeing so far.
upload_2020-8-4_16-38-39.png

The larger gage red insulated wire may have a fusible link at the battery positive or the starter relay terminal.

As 67Dart273 explained, the heavy black wires are also 'hot'.
The white 'bullet' connectors at the end of each clearly mate with the heavy brown wires.
I'm willing to bet that one of those brown wires connects the alternator output;
And the other heavy brown wire connects to the 16 gage blue fusible link which in turn leads to the standard main splice.
 
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I took a quick look at your postings and assume this is a '74 Dart Sport.
We've seen '73 Darts with electric defrost grids for the rear window with a differnt variation on the wiring your car has.

Assuming its a '74, below is the general scheme for standard power distribution.
upload_2020-8-4_17-0-19.png

The output wires from the Alternator and the Battery are joined with the feeds to the various circuits at a welded splice.
You can think of this as the power distribution point.
Most items use the chassis or engine block as the ground. The battery of course has connections to the block and the body. For the standard alternators, the housing is used, but these speciall 60 and 65 amp alternators sometimes had thier own ground wires.

Current flows like a stream. It flows either from the battery or the alternator to the main splice and then stream branches to whichever circuit(s) allow a return to ground.

Here's what it looks like we are seeing so far.
upload_2020-8-4_17-30-9.png


I'm not clear about the second black wire on the ammeter's stud (white arrow pointing to it).
Maybe I'm misunderstood your description of the wires joined, or is it a third as I sketch?
upload_2020-8-4_17-34-4.png


The white tag in the circle has the part number for the harness - so that probably can be looked up.

Let's redraw the sketch slightly so its more readable in terms of how it operates.
Even if the wiring connectoins on yours are a little different, the concept will be the same.
upload_2020-8-4_17-44-55.png


When the engine is running current flows to the junction on the ammeter's stud, then
IF the battery needs recharging, a portion of the stream splits off.
The rest of the current flows to the main splice.
upload_2020-8-4_17-57-2.png


The arrows in the sketch are illustrative of maybe 25 amps flowing in wire R6.
The ammeter indicated about 15 amps flowing through the battery for recharging. The remaining 10 amps are flowing through the ignition, alternator field, and whatever else is using electricity.
 
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Thank you @67Dart273 and @Mattax. Those diagrams are making a lot more sense with your explanations. I had the wiring diagrams in my Haynes manual for the car but when looking at those I always find it confusing with the diagrams being so busy. As Mattax mentioned the car is a 74 Dart Sport with a 225 and a904. As far as I can tell, the last diagram that Mattax posted makes the most sense. The other wires on the black ammeter side run to somewhere under the dash, possibly fuse panel, but I havent investigated at this point. The 2 brown wires did plug directly into the 2 black ones, I was just confused as to why. There is 1 brown larger wire running from the alternator output and is welded to both of those smaller brown connections up near where they enter through the firewall. Those diagrams helped me clear a lot of this up.
 
Well post more pics of what is there and do some continuity checks before hooking the battery up.
Especially this
Holden Customs said:
There is 1 brown larger wire running from the alternator output and is welded to both of those smaller brown connections up near where they enter through the firewall.
Click to expand...
Sure want the main power feeds connected properly!
Also if the car has an alternator alternator that uses a non-standard regulator and wiring, it would be good to know that sooner than later.

The diagram I drew only based on what I can figure from what you've posted and the various versions I'm aware of.
Holden Customs said:
The other wires on the black ammeter side run to somewhere under the dash, possibly fuse panel, but I havent investigated at this point.
Click to expand...
So it is a third connection!?
One possibility is rear window defroster. Was this car so equiped?
Another possibility is that it runs to the main splice.
I suppose it is also possible to run to the fuse box - perhaps for a dedicated fuse for something.

Finally, look for another fusible link on the battery line, possibly near the starter relay. It likely will not be blue, but probably has a flag on it.

Continuity checks. This is a method of figuring out what connects.
Disconnect the wires at the connectors of interest. Then measure for continuity from one terminal to where you think the other end of the wire connects.
 
Mattax said:
Continuity checks. This is a method of figuring out what connects.
Disconnect the wires at the connectors of interest. Then measure for continuity from one terminal to where you think the other end of the wire connects.
Click to expand...

Example.
Take an ohm meter or a continuity light.
Touch one probe or clamp to one of the brown wires.
Touch the other one to the alternator output terminal.
upload_2020-8-5_0-56-35.png


If it shows continuity, then you've found the wire that connects to the alternator output.

Then knowing the other one probably connects to the main splice, see if the unknown black wire also connects to the main splice.
The second probe can clip on at the starter relay (shown) or better yet, one of the black wires going directly to the ammeter's post.

upload_2020-8-5_0-50-20.png

If there is continuity, then the mystery wire somehow connects to the main splice.
If there is no continuity, then it doesn't.

PS. The data plate on the fender may clue in to what options the car came with. Also whether it was a Canadian build - which in some cases were different. If its a Canadian build, you may need the Canadian shop manual. So far what you have found looks more like the drawings for an earlier version.
The 18 ga yellow wire may be aftermarket or may be somehting like a clock option. That's where the clock was wired in '67-?
 
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@Mattax To address some of your questions. I know the car was a canadian build, and yes it does have a rear window defroster which could be that mystery wire. The 18ga yellow wire runs to a switch and relay which wasnt stock, looks to be for an aftermarket something or other. I was going to use it for a fuel pump but I will re-wire the feed properly from a better source. There is a fusible link in the larger red wire you labelled as "from battery" at the ignition relay. The 16ga one you had circled with the blue tag and link runs to the ignition relay aswell but it goes directly to the coloumn connection after the firewall. I will have to do all the continuity checks and get some more pictures in a couple weeks as I am out of town for work. But I appreciate all the help so far. Its making more and more sense.
 
Holden Customs said:
There is a fusible link in the larger red wire you labelled as "from battery" at the ignition relay.
Click to expand...
Thanks. Red or Red with tracer, or green? Chrysler's color designates a wire gage of the link.

Holden Customs said:
The 16ga one you had circled with the blue tag and link runs to the ignition relay aswell but it goes directly to the coloumn connection after the firewall.
Click to expand...
Very interesting! It's possible Chrysler Canada seperated the power feed to the key switch from the power feeds that are always hot. We see this on '76 A-bodies.
Holden Customs said:
I was going to use it for a fuel pump but I will re-wire the feed properly from a better source.
Click to expand...
Electric fuel pumps can be an issue with the standard wiring strategy and alternator. Even with the very rare option that your car seems to have I'd encourage you to consider using a mechanical pump if you can. If you'er thinking boosted of some sort, keep in mind Studebaker ran a supercharger with a mechanical pump - so it may be possible in your application as well.... Just somehting to think about.

Holden Customs said:
is there a program you are using for these wiring diagrams? Seems like a useful tool
Click to expand...
Generally using two very basic programs.
IRFAN shareware. IRFAN has two components. One is "Thumbnails" which allows bulk changes to images, such as resizing, creating resized files with new names and watermarks, etc. The second componenet is Irfanview. It can be opened from a thumbnail or on its own. Images can be marked up and saved in various formats. it also has a screen capture function. There's a small learning curve for Irfanview. A bigger learning curve for bulk operations.

MS Paint. This came with either Windows 7 Pro or maybe I moved a copy over from Win XP. I forget.
Its particularly good for cutting and pasting within a drawing.

For example this is a screenshot of the B-body engine compartment wiring from a pdferized '73 shop manual.
upload_2020-8-5_16-12-10.png


I started by colorizing the circuits of interest. In this case the 60 amp alternator wiring.
Irfanview is good for this beause it has good line size control.
upload_2020-8-5_16-13-38.png



But then to cut away all the unrelated items, and move the items around, Paint is the better program.
upload_2020-8-5_16-18-6.png


Eventually end up with something like this
upload_2020-8-5_16-20-43.png


Notice in this particular version the alternator and voltage regulator wiring is the same as a standard Chrysler.

In contrast the 65 amp alternator, same year, same car lines, is different. It's probably a Leece Neville built alternator.
upload_2020-8-5_16-24-9.png
 
You might mention that in that last diagram you have shown the infamous 65A optional "police fleet taxi" wiring which bypasses the bulkhead connector for the majority of the current
 
@Mattax The larger red wire that runs to the ignition relay has a blue tag and blue link.

Thanks for the info on the programs. I have used MSPaint a lot but I havent heard of the other ones. I will have to look them up.
 
@Mattax I am also fairly certain this car did not use the 65A alternator. The old one I got the car with wasnt anyway.

Unfortunately I am not able to use a mechanical pump in my application. I will be installing a holley sniper 2300 shortly that needs 58 psi, as well as adding a turbo shortly down the line.
 
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